Arsenal Mercenary
Last Updated: 5/31/21
Table of Contents
Overview
About the Class
Arsenal is a burst DPS class that can also provide decent sustained DPS. They excel in target swapping. They do well in fights with mobility. With great survivability and good DPS, a skilled Arsenal player may not match the top-end DPS of some classes but can more than hold their own in Hard Mode Ops.
Utility and Mobility
With proper utilities, every Arsenal ability is instant or can be used on the move except for Tracer Missile. Unfortunately, Tracer Missile is the most frequently used ability in the rotation. Use of Power Surge (w/ Utility) can enable 2 instant casts, and using Priming Shot will enable 1 instant cast. In fights with lots of mobility, a Arsenal player may have to use a basic attack occasionally but generally can maintain very good DPS on the move with practice.
Survivability
Mercenaries have great survivability. Except for classes that include a tank discipline, they are the only DPS class that wears heavy armor. As a class with a healing discipline, they possess good off healing capability for emergencies. They also possess a wide range of useful defensive abilities that include a straight buff to DR, an emergency sustained self heal and a powerful reflect. Arsenal also contains a really cool defensive via its threat drop ability due to a passive skill tree ability.
Role in Operations
Arsenal has flexibility regarding target assignments and is frequently a good choice to deal with adds. Combining heavy armor, good defensive CD’s, off-heals, and skills-utilities buffing mitigation and healing received, Arsenal should also provide a very durable DPS player.
6.1.2 Impact on Discipline
Arsenal was nerfed in patch 6.1.2 via the removal of the +10% critical chance buff from the Concentrated Fire set bonus. The nerf was primarily intended towards Mercenary healers but affected Arsenal as well. As such, Apex Predator should now be the best in slot set bonus choice for Arsenal as it provides a strong buff to your primary filler, Tracer Missile, in comparison to a much weaker Concentrated Fire set bonus after the nerf.
Utilities
I usually take some combination of the following Utilities, though the optimal combination can change from fight to fight. As of 6.0, the tiers have been reorganized.
Skillfull Tier
You must take 3 to advanced to Masterful.
Improved Vents - Vent Heat now immediately recharges 15 additional cells and grants 10% alacrity for 6 seconds.
Must take, more energy = more DPS.
Gyroscopic Alignment Jets - You recharge 20 cells when stunned, immobilized, knocked down or otherwise incapacitated. Also, when incapacitated, your next Tech ability deals 10% damage or healing. This effect lasts for 15 seconds.
Situational, used for fights with lots of stuns or knockbacks as it will significantly increase DPS by using more high-energy high damage fillers. Given the lack of good choices in Skillful, I would nearly always take this utility.
Boresights - Increases the damage dealt by Sweeping Blasters by 25%. Situational, great for boosting AoE DPS but skillful DoT spread should handle AoE damage to a sufficient degree.
I don’t care for this utility but it remains the best available out of a pool of poor remaining choices. Threat Sensors should not generally be taken by a DPS player, so I am usually left with this utility to finish out the tier.
Threat Sensors - Increases stealth detection, melee and ranged defense by 3% and reduces the cooldown of Stealth Scan by 5 seconds. Also, when you activate Cure on yourself, all periodic damage taken is reduced by 30% for 12 seconds.
A DPS player should generally not be cleansing themselves (leave that to the healers and spend the GCD on more DPS), but in some limited instances this could be useful.
Masterful Tier
You must take 6 between Heroic and Masterful.
Power Overrides - Reduces the cooldowns of Concussive Missile and Power Surge by 15 seconds each. Also, Power Surge grants a second charge, making your next two abilities with an activation time activate instantly.
A very useful utility for Mercenary DPS players. Both DPS disciplines feature an instant proc of their filler attack used in the rotation. When/if that proc does not line up, this utility can help prop up the rotation. It can also be very helpful when DPSing on the move.
Torque Boosters - Increase the duration of Hydraulic Overrides by 4 seconds.
I usually take it as a longer duration for Hydraulic Overrides grants significant extra movement speed in fights and can be very helpful on many fights.
Energy Rebounder - When you take damage, the active cooldown of Energy Shield is reduced by 3 seconds. This effect cannot occur more than once every 1. Seconds. Also, when taking damage, you have a 20% chance to emit an Energy Redoubt which absorbs a low amount of damage and lasts 6 seconds. This effect cannot occur more than once every 10 seconds.
Frequently take, this can drastically reduce the cooldown on a key defensive.
Power Barrier - Power Shot , Tracer Missile, and Rapid Scan build a Charged Barrier that reduces damage taken by 1% for 15 seconds. Stacks up to 5 times.
I usually take, a good utility that will grant you 5% extra DR for the majority of most boss fights, helping survivability. I always take for any fights where Torque Boosters is not needed.
Pyro Shield - When activated, your Energy Shield charges with electricity, zapping attackers for elemental damage when they deal direct damage to you. This effect cannot occur more than once each second.
Situational, there are some fights where this utility would be useful and preferred over Power Barrier.
Heroic Tier
A maximum of 3 utilities
Thrill of the Hunt - Allows Unload, Blazing Bolts, and Progressive Scan to be activated while moving.
Always take, being able to channel on the move is a massive boost to your mobility and is the most essential utility for this class.
Stabilized Armor - Reduces damage taken from area effects by 30%. Also, while stunned, you take 30% less damage from all sources.
Must take, 30% AOE and stun damage reduction is massive.
Kolto Surge - Kolto Overload triggers at, and can heal you up to, 60% of your maximum health. Also, Kolto Overload lasts 2 seconds longer and heals for twice as much each time it restores health.
I usually take, I love this utility for any operation with lots of raid-wide damage. If you get low on health but the healers are swamped and trying to burst-heal a tank to keep them alive, then as long as you don’t eat any big damage spikes you don’t need any heals for 12 seconds (and generally will still be in decent 50-60% health after 12s). When used with skill, this makes Kolto Overload a HUGE survivability boost over its existing capabilities. Absent an enrage or other high damage AoE or mechanic, I never die when I hit Kolto Overload with this utility.
Trauma Regulators - While Energy Shield is active, you generate a stack of Trauma Regulators each time you receive direct damage. Stacks up to 10 times. When Energy Shield expires, each stack of Trauma Regulators instantly heals you for 4% of your maximum health.
Don’t usually take as while a 40% potential heal sounds nice, you need Energy Rebounder for this to be meaningful and Stabilized Armor will usually reduce your damage taken by more than this utility will heal you.
Example Utility Build
Here is what I run for most encounters, though I frequently take other situational utilities for specific fights.
Key Passives
High Velocity Gas Cylinder - Loads your rifle with an armor-piercing cell. While active, armor penetration is increased by 35% and alacrity is increased by 3%.
This passive is the base ability for the discipline, which focuses on armor penetration to deal heavy damage by bypassing enemy armor moreso than most other disciplines. The 3% alacrity bonus also makes it cheaper on a stat budget to achieve desired alacrity GCD breakpoints.
Tracer Lock - Tracer Missile grants Tracer Lock, increasing the damage dealt by the next Rail Shot by 6% or reducing the activation time and increased the healing dealt by the next Rapid Scan by 20%. Stacks up to 5 times.
This passive drives a key feature of the discipline’s rotation which is to use Rail Shot nearly on cooldown and with as many stacks of Tracer Lock as possible to get the full 30% damage buff.
Terminal Velocity - You passively regenerate 2 energy cells every 1.5 seconds. In addition, the amount of heat generated by Rail Shot is reduced by 10.
This passive is critical to the discipline's energy management by increasing "fast" energy regeneration from 5 per second to 7 and making a key filler net positive for energy regeneration.
Honed Lock - Tracer Lock increases the critical chance of the next Rail Shot or Rapid Scan by 3 per stack.
Related to Tracer Lock, this passive adds a critical chance buff of 3% per stack up to a maximum of 15%. Thus, using Rail Shot with 5 stacks of Tracer Lock grants +30% damage and +15% critical chance.
Burst Mode - Armor penetration granted by Supercharged Gas is increased by 5%, and Supercharged Gas stacks build twice as fast and can build 3 additional stacks.
A passive to further increase armor penetration and improving energy management through more frequent uptime of Supercharge stacks.
Ironsights - Increases the damage dealt by grenade attacks, round attacks, and Priming Shot by 10%. Also, Priming Shot marks its target, causing it to take 5% more damage from ranged attacks.
This passive provides an overall damage buff and an important debuff that will improve the effectiveness of most of the discipline’s attacks.
Decoy - Diversion grants 2 charged of Decoy. Each charge of Decoy intercepts and absorbs an incoming Force or tech attack. Each time you absorb a Force or tech attack in this manner, Decoy loses 1 charge. Lasts up to 10 seconds.
This passive is really neat for mitigation purposes. Decoy now becomes a cheese ability for highly damaging Force/Tech attacks. A great example are the orbs in Brontes Hard/Master Mode in the Dread Fortress operation. Combined with the already great class defensives, Arsenal is a very strong discipline from a survivability perspective.
Barrage - Tracer Missile and Sweeping Blasters finish the cooldown on Blazing Bolts. This effect cannot occur more than once every 8 seconds.
The most important passive ability to the discipline, it provides for the proc of Blazing Bolts. This drives the priority rotation and its goal to trigger this passive ability as close to every 8 seconds as possible, even while Blazing Bolts may not be immediately used due to higher priority abilities.
Gearing in 6.0
Gearing Stat Allocation
Please see my Gearing Guide and Alacrity Guide for a detailed overview of gearing in 6.x in SWTOR.
For Arsenal Mercenary, I gear as follows:
Set Bonus: Apex Predator (Concentrated Fire is okay if you primarily run Innovative Ordnance)
Tactical: Primed Ignition (Thermonuclear Fusion for AoE)
Amplifiers: Armor Penetration
Mods: Unlettered Lethal Mods
Relics: Devastating Vengeance & Primeval Fatesealer (Serendipitous Assault & Focused Retribution for Dxun/PVP)
Stim: Proficient
Adrenal: Critical (Attack for Dxun only)
For Arsenal Mercenary, I allocate my tertiary stats as follows:
Accuracy: 1,585 - 1,630 (anything outside this approximate range and I usually try to re-optimize by swapping around enhancements and augments)
Alacrity: around 2,550 for high alacrity, a secondary option is around 850 for low alacrity (at least 2,000 if the Zeal guild perk applies)
Critical: all remaining tertiary points go into Critical
Shield: None
Absorb: None
Set Bonus
Concentrated Fire
Increased drop rate from PVP.
(2) +2% Mastery
(4) Damaging an enemy or healing an ally has a 10% chance to generate a stack of Supercharge. This effect cannot occur more than once every 5 seconds.
(6) Activating Supercharged Gas makes your next Rail Shot, Mag Shot, or Emergency Scan critically hit or heal.
Analysis:
Concentrated Fire was nerfed in patch 6.1.2 to remove its previous 4-piece set bonus that provided +10% critical chance with extremely high uptime. The previous six piece set bonus was split out into the new 4 and 6 piece set bonuses. The remaining set is much weaker as a result. The extra Supercharge is nice but is unpConcentrated Fire was nerfed in patch 6.1.2 to remove the four piece bonus that provided very high uptime on a +10% critical chance buff. The old six piece bonus was split into the new four and six piece bonuses. The set is far weaker as a result and unlikely to be best in slot for Mercenary DPS, particularly Arsenal.
The primary weakness of the set bonus is the infrequent nature of its benefits. An auto-crit is nice but being triggered by Supercharged Gas is infrequent enough that its benefits are diluted in terms of DPS impact. Similarly, the 10% chance to generate Supercharge is helpful in theory but unable to be controlled. Even assuming that a DoT is ticking to provide multiple ticks of damage each GCD and thus multiple rolls at the 10% Supercharge chance, it seems unlikely the four piece will trigger more often than every 8-10s seconds on average (so 3-5 seconds after it becomes possible to trigger it from the internal cooldown). That translates to an extra Supercharged Gas once every 80 - 100 seconds, or 2 - 3 extra Supercharged Gases each fight. Again, that’s not a bad DPS benefit but it pales in comparison to the previous Concentrated Fire.
As such, I recommend Apex Predator as it provides more consistent benefits via its steadily increasing critical chance on Tracer Missile and periodic free boosted use of Tracer Missile. Had the developers wanted Concentrated Fire to be a stronger option, I would have preferred a feature that let you control when the extra Supercharged Gas was available such as using Thermal Sensor Override to instantly generate 10 Supercharge (or something similar). That would lead to the same overall uptime but much better control for back-to-back Supercharge Gas windows and be far more powerful as a burst DPS option.
Impact on Rotation:
No change on rotation.
When to Take:
Not recommended unless Apex Predator is not available. If so, Concentrated Fire is a decent alternative.
Apex Predator
Increased drop rate from Dxun operation Nature of Progress. Not available to purchase at Tech Frag vendor.
(2) +2% Mastery
(4) Activating Power Shot, Tracer Missile or Rapid Scan increases the critical chance of your next Power Shot, Tracer Missile or Rapid Scan by 10%. Stacks up to 5 times but is removed on 6th stack.
(6) Dealing damage with Power Shot or Tracer Missile or healing with Rapid Scan grants a stack of Power Step, stacking up to 5 times. At 5 stacks, your next Power Shot, Tracer Missile or Rapid Scan is more effective and generates no Heat.
Analysis:
Apex Predator was not changed by patch 6.1.2 but was the beneficiary of the nerf to Concentrated Fire. It is the strongest set bonus available for Arsenal Mercenaries. It's four and six piece bonuses provide a significant boost to the damage of Tracer Missile, which is used often in the Arsenal rotation. The energy savings of getting an occasional free Tracer Missile is also quite helpful to the discipline's energy management, which can be tricky to properly time a proc for Blazing Bolts.
Impact on Rotation:
No change to priority rotation. The set bonus will boost damage to Tracer Missile and make every 6th use free of energy cost, which is helpful to the rotation and enabling more frequent use of Tracer Missile but does not elevate it above any other abilities in the priority.
When to Take:
Recommended over Concentrated Fire assuming it is available.
Tactical Items
Primed Ignition
Increased drop rate from operations.
Priming Shot causes its target to burn. Blazing Bolts, Heatseeker Missiles, Priming Shot, and Tracer Missile all tick its damage.
Analysis:
This is a great tactical for Arsenal and is a huge reason why the discipline has much better sustained damage in 6.0. Adding a DoT and being able to tick its damage through nearly all rotational abilities adds a lot of DPS. Theorycrafting and personal parsing experience suggests it should comprise around 20% of total DPS in a high quality parse, making it a 25% increase in damage compared to DPS without the tactical equipped. This buff vastly outweighs Burning Bright as a single target option and so is the preferred tactical for all fights except those with heavy and nearly constant AoE damage requirements (e.g., Hive Queen, Dxun Holding Pens, Dxun Security Center, etc.)
Impact on Rotation:
Priming Shot becomes the third priority ability only behind (1) using Blazing Bolts before proccing it again; and (2) using Tracer Missile to proc Blazing Bolts every 8s. In terms of all other abilities, Priming Shot takes top priority to apply the Primed Ignition DoT.
When to Take:
All situations except for extremely heavy AoE encounters.
Thermonuclear Fusion
Increased drop rate from flashpoints.
Fusion Missile spreads your Tracer Missile's Heat Signature to the targets it damages, as long as it damages at least one target already affected by your Heat Signature. Heatseeker Missiles fire additional missiles to nearby targets affected by your Heat Signature.
Analysis:
Fusion Missile is already a helpful AoE DoT ability that should be used in AoE rotations. Adding in the capability to make Heatseeker Missile an AoE finally gives Arsenal semi-decent AoE potential for a change.
Impact on Rotation:
In single target situations, nothing should change in that Fusion Missile is not used and this tactical provides no benefit. In AoE situations, make sure to use Fusion Missile AFTER Tracer Missile but BEFORE Heatseeker Missiles. The revised opener would go as follows:
Tracer Missile
Fusion Missile (spreads debuff from Tracer Missile)
Heatseeker Missiles (now an AoE ability)
Blazing Bolts
(Power Surge) - normally not needed but used in this revised opener
Tracer Missile (proccing Blazing Bolts)
Priming Shot
Tracer Missile
Tracer Missile
Rail Shot
Blazing Bolts
Tracer Missile (proccing Blazing Bolts)
Heatseeker Missiles (now an AoE ability)
{continue priority rotation}
When to Take:
Recommended for any heavy AoE situations, especially if the group does not have many DPS with exceptional AoE capabilities independent of tactical item choices (i.e., primarily DoT-based disciplines with DoT spreading).
Burning Bright
Increased drop rate from flashpoints.
Dealing damage with Blazing Bolts increases the damage of your next Priming Shot, stacking up to 4 times to 100%.
Analysis:
This tactical provides incremental extra burst damage potential via buffing Priming Shot. I rarely utilize this tactical because in practice it only buffs Priming Shot by 25-50% given its cooldown in relation to the frequency of Blazing Bolts. It is not worth delaying Priming Shot in a sustained damage situation for the extra buff.
As such, I feel like this tactical is only useful for (1) PvP, where you could more reasonably save the 4 stack until you get someone low in health and then deal a huge amount of burst damage; or (2) PVE encounters with exceptionally high burst window checks. With that said, there are no DPS burst checks that are high enough to require this type of maneuvering while having low enough sustained DPS check to enable delaying a high damage ability for a burst window.
Impact on Rotation:
No change in most situations. Use Priming Shot on cooldown except for higher priority abilities as per normal priority.
When to Take:
Not recommended for any situations.
Amplifiers
Armor Penetration (or Weapon Expertise / Periodic Intensity as secondary options)
All damage is Energy/Kinetic except the Elemental DoT applied by Priming Shot via the Primed Ignition tactical. As such, Armor Penetration provides significantly more boosts to DPS than other alternatives.
Weapon Expertise should provide the next best boost to DPS, primarily due to Blazing Bolts dealing weapon damage and being the highest DPS ability. Periodic Intensity is a distant third for Arsenal as it primarily buffs the Priming Shot DoT.
If you are looking to synergize the best amplifier build to run both Arsenal and Innovative Ordnance, I recommend Armor Penetration or Periodic Intensity. Armor Penetration is the best for Arsenal by a large margin, while Periodic Intensity is the best for Innovative Ordnance. If you run one discipline significantly more often than the other then balance your amplifier towards that discipline. If you run them equally, you should receive the best DPS boost from Armor Penetration by a small amount.
Key Abilities
Blazing Bolts - Channelled attack over 2 GCDs dealing high damage. 15 second cooldown but can reset cooldown through Barrage passive ability every 8 seconds.
The highest damage ability for Arsenal and signature ability for the discipline. As discussed below, the entire main focus of the rotation is using this ability as often as possible by proccing it every 8s with Tracer Missile via the Barrage passive ability.
Heatseeker Missiles - High damage ability, deals 25% more damage if target is affected by the debuff applied by your Tracer Missile.
The highest damage filler ability and highest damage in one GCD, it takes high priority.
Electro Net - Instant filler should be applied on cooldown.
A strong and energy efficient damage ability. It has a long cooldown so is only used infrequently in the rotation but should be prioritized when it is available.
Rail Shot - High damage ability, 15 second cooldown, damage is buffed by stacks of Tracer Lock.
A key damaging ability that is buffed through uses of Tracer Missile to deal additional damage and increased critical chance. It should be used on cooldown with as many stacks of Tracer Lock as possible.
Priming Shot - High damage ability, 18 second cooldown, procs Tracer Missile to be instant the next time it is used.
A high damage filler ability that procs Tracer Missile to be instant. Depending on your choice of tactical, this will either by your top priority filler to apply a DoT or the lowest priority filler. It is important in the rotation and bears additional attention since proccing an instant Tracer Missile can alter the timing of when Blazing Bolts can be procced.
Tracer Missile - Spammable filler ability, applies Sundered debuff (reduces armor by 20%), resets the cooldown of Blazing Bolts via the Barrage passive ability, and builds stacks of Tracer Lock. Builds 2 Supercharge.
Your general filler ability is very important. It deals relatively high damage for a filler cast, applies an armor debuff that also significantly boosts the damage potential of Heatseeker Missiles, applies stacks of Tracer Lock to buff the damage of Rail Shot, and procs to reset the cooldown of Blazing Bolts. The ability should be frequently used but avoiding using it too much is critical to avoid energy issues.
Supercharged Gas - Converts 10 stacks of Supercharge to regenerate 10 units of energy and provides a buff unique to each discipline. For Arsenal, Supercharged Gas increases armor penetration by 10% for 8s.
The discipline's low cooldown energy management and offensive cooldown ability. It should generally be used on cooldown except when a burst damage phase is imminent.
Rapid Shots - Free spammable basic ranged attack, builds 1 Supercharge per use.
Your basic filler ability. It should be used occasionally in the rotation as a substitute for Tracer Missile to manage energy. The key skill for making the rotation work is knowing when you can safely swap in a basic attack to avoid energy issues.
Cooldowns & Other Abilities
Cure - Cleansing ability, use when necessary
Emergency Scan - Cheap and powerful instant cast heal
Rapid Scan - Spammable moderate heal. Builds 2 Supercharge.
Chaff Flare - Reduces threat towards all current enemies. 45s cooldown.
Vent Heat - Rapidly restores 50 energy over 3 seconds. Most powerful energy cooldown. 1:30 cooldown.
Thermal Sensor Override - Your next ability costs no energy. Lasts 15 seconds. 1:30 cooldown.
Power Surge - Your next ability used within 15 seconds with an activation time will activate instantly and then grant immunity to pushback and interrupts for 6 seconds. 1:00 cooldown.
Hydraulic Overrides - Grants 6 seconds of immunity from movement-impairing effects, knockdowns and physics and increases movement speed by 30%. 45s cooldown.
Energy Shield - Increases damage reduction by 25% for 12 seconds. 2:00 cooldown.
Responsive Safeguards - Absorbs all incoming single target direct damage for the next 6 seconds and reflects 50% of the absorbed damage back at the attacker and healing you for 5% of your maximum health each time an attack is absorbed. Can be used while stunned. 2:00 cooldown.
Kolto Overload - Applies a Health Monitor that lasts 60 seconds, which triggers Kolto Overload when your health is reduced to 35% or less. If your health is already 35% or less, it triggers immediately. Once triggered, it goes on cooldown for 3 minutes and rapidly heals you up to 35% of your max health for 10 seconds but will not exceed 35% of your max health.
Rotation
Opener
6.0 NOTE: This opener and rotation assumes the player is using the Primed Ignition tactical. If not using this tactical, the priority for filler abilities will be slightly different as Priming Shot becomes your lowest priority versus being the filler priority with the tactical and as presented below.
1
3
5
7
9
11
13
15
2
4
6
8
10
12
14
16
Tracer Missile - We lead with a hard cast of Tracer Missile to apply the armor debuff that will make all other abilities do more damage.
Adrenal OFF GCD - We start dealing very heavy burst damage immediately so hitting all cooldowns up front.
Supercharged Gas OFF GCD
Priming Shot - Prioritized filler due to Primed Ignition tactical to apply the DoT
Heatseeker Missiles - Next priority filler as it deals very heavy damage
Electro Net - Last priority filler
Blazing Bolts - We have used 3 GCDs of fillers since Tracer Missile so need to channel here so we can immediately reset its cooldown again next ability
Tracer Missile - Should be an instant cast via the earlier use of Priming Shot, should also proc Barrage and reset the cooldown of Blazing Bolts, also increases our stacks of Tracer Lock from 2 to 4.
Tracer Missile - Filler ability, increases our stacks of Tracer Lock to a max of 5.
Rail Shot - Used with 5 stacks of Tracer Lock to maximize damage and critical chance
Thermal Sensor Override OFF GCD - We avoided energy issues earlier via the upfront use of Supercharged Gas, so we use here prior to Blazing Bolts to get the maximum energy recovery right as we start to get near to a breakpoint on energy levels.
Blazing Bolts - We reset its cooldown 3 GCDs ago, so need to use here so we can continue to reset its cooldown as quickly as possible
Tracer Missile - Earliest GCD we can reset the cooldown of Blazing Bolts again, so top priority to use here
Tracer Missile - No other priority ability off cooldown so used here
Heatseeker Missiles - Used off cooldown
Blazing Bolts - Need to use here before we reset its cooldown again
(continue priority rotation)
Single Target Priority Rotation
1
Tracer Missile (if proccing Blazing Bolts).
Barrage enables Tracer Missile to proc Blazing Bolts and increase its damage +10% every 8 second. Blazing Bolts is your highest damage ability, so proccing it as often as possible is the most important priority. Since you will be channeling Blazing Bolts in that window, that means you can use Blazing Bolts and 2-3 other abilities.
The best way to think about Blazing Bolts by # of GCDs. 8 Seconds to proc Blazing Bolts equates to either 5 GCDs if you are hardcasting Tracer Missile (i.e., the proc occurs at the END of the GCD) or 6 GCDs if you are proccing Tracer Missile via Priming Shot or Power Surge.
2
Blazing Bolts (if you can need to use Tracer Missile in 2 GCDs to proc Blazing Bolts)
See the discussion above at #1 regarding the use of Tracer Missile. The overall goal of the rotation is to use Blazing Bolts as much as possible. However, the fastest you can ever use this powerful attack is every 8s because that is the rate limit for triggering Barrage. As such, it does not matter if you use Blazing Bolts as soon as it procs or just before proccing it again.
As discussed further below regarding the use of Tracer Missile to proc Barrage to reset the cooldown of Blazing Bolts, you will have either 6 GCDs or 7 GCDs between procs depending on whether you hard cast or instant cast. If you have not already used Blazing Bolts by the time only 2 GCDs are left before you need to proc it again, it takes absolute priority. You do not want to waste a use of Blazing Bolts.
3
Priming Shot (with Primed Ignition tactical)
After the core goals are handled to make sure you are using Blazing Bolts every 8s through timely proccing of Barrage, you then get into priority for high damage fillers.
Priming Shot takes top priority if you are using the Primed Ignition tactical due to the damage dealt and the DoT applied by the tactical. You want as much uptime on that DoT as possible as it provides a significant buff to the discipline's sustained damage output.
A key consideration when using Priming Shot is whether the instant cast it provides for your next use of Tracer Missile will impact the timing to proc Blazing Bolts. As discussed further below, if you use Tracer Missile on the 6th GCD expecting to proc it via a hard cast then the instant cast could fail to proc it and disrupt the rotation and energy management by forcing a second Tracer Missile.
4
Heatseeker Missiles
A very high damage ability that should be used on cooldown. The only consideration is to make sure Tracer Missile has been applied first, as its debuff will enable Heatseeker Missile to deal 25% more damage in addition to the damage increase provided by its armor debuff.
5
Electro Net
Electro Net is a high damage and energy efficient ability. It has a very long cooldown so is not used that often typically.
6
Rail Shot (with 4-5 stacks of Tracer Lock)
Ideally Rail Shot should only be used with 5 stacks of Tracer Lock. However, a key element to maximizing DPS on this discipline is knowing that is is frequently optimal to use Rail Shot on cooldown with 4 stacks rather than delaying 2-3 GCDs for other priorities.
7
Blazing Bolts
If it's confusing to see Blazing Bolts on this list twice (and one being fairly far down), remember that our ability to use the ability is limited to no more often than every 8 seconds. The only time we want to use Blazing Bolts is when other abilities are on cooldown or when it's nearly time to proc it again.
The pattern this usually follows in a fight is that after you use Tracer Missile to proc Barrage, your high priority fillers (Priming Shot, Heatseeker Missiles, Electo Net and Rail Shot) are on cooldown. In that case, use Blazing Bolts right away to make room later to use the fillers as they come off cooldown before proccing Blazing Bolts again.
8
Tracer Missile (if not proccing Blazing Bolts and have excess energy)
You can use Tracer Missile as a general filler when all other abilities are on cooldown, you cannot proc Blazing Bolts, and have excess energy. Be very careful about extra uses of Tracer Missile as that is the way newer players most frequently get into energy trouble. When in doubt, skip this priority and go to your basic attack instead.
9
Rapid Shots (if unable to proc Blazing Bolts and do not have excess energy)
Used when everything else is on cooldown, you cannot proc Blazing Bolts that GCD with Tracer Missile, and do NOT have excess energy for an extra cast of Tracer Missile.
Proccing Blazing Bolts
As a reminder and quick recap, Blazing Bolts can have its cooldown reset every 8s by using Tracer Missile via the Barrage passive ability.
The overall priority for the rotation is to use Blazing Bolts as much as possible by proccing it as close to every 8s as possible. As discussed above, this priority does not always mean using Blazing Bolts on cooldown but instead using Tracer Missile every 8s or as close to is as possible to get the proc.
The aspect of this rotational goal that makes it difficult to achieve is the odd cooldown timer of 8 seconds. Assuming no alacrity, 5 GCDs will take up 7.5s while 6 GCDs will take up 9.0s. So that gives us a 6 GCD cycle for each proc that needs to use 2 GCDs to channel Blazing Bolts and 1 GCD to cast Tracer Missile to get the proc at the end of the window. That leaves 3 GCDs for fillers.
Adding another wrinkle is the impact of Priming Shot or using Power Surge. Both cause Tracer Missile to be instant cast. This is important because it changes the timing of the proc.
Normally Tracer Missile triggers the Barrage proc at the END of the cast/GCD. When the ability is instant, the proc triggers at the BEGINNING of the GCD. Using an instant proc Grav Round on the 6th GCD will NOT proc Blazing Bolts since the proc happens at 7.5s assuming no delay between ability activations. Even worse, now we have to hard cast a second Tracer Missile that procs Blazing Bolts at the end, taking 11.5 seconds to get the proc instead of the usual 9s.
So what's the takeaway here? There are two scenarios that guide your "rotation" in terms of how often to use fillers versus using Tracer Missile to proc Blazing Bolts, which are entirely dependent on whether Tracer Missile is a hard cast or instant cast:
Hard Cast Tracer Missile: 3 filler abilities, 1 Blazing Bolts, then hard cast Tracer Missile
Instant Tracer Missile: 4 filler abilities, 1 Blazing Bolts, then instant cast Tracer Missile using either Priming Shot or Power Surge
Energy Management
Always use Thermal Sensor Override on Blazing Bolts. This channeled ability takes 2 GCDs so using the cooldown here grants more free energy regeneration than any other ability and offsets the most expensive individual ability (20 energy cost). This grants you the most energy regeneration for the ability use as compared to any other option.
Make sure to get the full benefit from Vent Heat cooldown and its buff from the Improved Vents utility. This ability regenerates 65 energy over 3 seconds. Along with natural energy regeneration during those 3 seconds of anywhere from 6 to 15 energy, you can hit this cooldown when at 20-25 energy cells / 75-80 heat and get all the way back into a good energy position. Do not hit it as soon as you drop below optimal energy regeneration levels or you will waste a lot of free energy. This is the difference between an extra 8-10s of heavy burn so take full advantage and get some practice on a dummy to get the feel for when to hit it.
Avoid over casting Tracer Missile and make sure to use Rapid Shots periodically. The optimal ability usage over an extended period should be about energy neutral without any energy cooldowns. When you consider Supercharged Gas that is used rotationally, you should be able to use the occasional Tracer Missile as a filler in addition to the cast that is used to proc and reset the cooldown of Blazing Bolts.
However, the easiest way to wreck Arsenal from an energy perspective is too much Tracer Missile spam. I suggest using Tracer Missile continuously when Vent Heat is available (or about to be), but otherwise being selective with its use. If I have Thermal Sensor Override, I can use 1-2 extra Tracer Missile casts. If I know Supercharged Cell is up or about to be, that's 1 extra.
If I have no energy cooldowns available, I try to alternate my use of Tracer Missile and Rapid Shots. Blocks where you use your big fillers can drop you in energy fairly quickly, so anytime I'm below 80 energy I try to prioritize Rapid Shots as well to protect against big drops from a block of big fillers.
Again, it's important to note that you should always prioritize Tracer Missile to proc Blazing Bolts. Just be careful to avoid lots of extra casts to maintain energy properly.