Asherre's Mercenary Healing Guide

How to not suck as a Mercenary Healer in PvE
--------------------------------------------
I. Stat Priorities
II. Talent Tree
III. Rotation
IV. Situational Abilities
   i. Power Surge
   ii. Kolto Shell
   iii. Rapid Shots
V. Conclusion
--------------------------------------------
I. Stat Priorities
One of the biggest and most important parts of playing a mercenary healer is your stats.
This is a part where most mercenary healers mess up, and a big reason why most merc healers will never be anything more than mediocre.
Let's address primary stats first. For armorings, you always want to go with the armoring with the highest aim and the lowest endurance.
For mods, you should go with the mod with the lowest endurance.

One major mistake made is to stack critical chance to a given percentage and then stop. Don't do this. It is not important what % you reach, but how far into diminishing returns for a stat you are.

As such, your first priority will be to stack critical rating to ~350. Critical rating is important not just for output, but to ensure that you can get "big heals" out. Critical heals are the heals that really move people's health bars. The success or failure of a raid can depend on how quickly you can get a critical heal out and bring the tank's health back up to safe levels. The lower your critical chance, the more heals on average this will take.

Once you have around 350 critical rating, all of your remaining secondary stats should be going into power.

The final part of statting is your tertiary stats. It is a common misconception that mercenary healers are supposed to stack alacrity. In reality, alacrity is one of the few stats that actually decreases a mercenary healer's maximum long term throughput. Though it allows for slightly more burst capability, burst is not the mercenary healer's strong suit, and any attempts to focus on alacrity will degrade your performance.

As such, your tertiary stat priority is as follows.

Surge >>>>>>>>>>>>> Accuracy >>>> Alacrity

Of course, this means you should only take Surge if possible, and if you cannot obtain Power/Surge or Crit/Surge enhancements, take Accuracy. Alacrity is a stat of last resort.

Some might argue that alacrity may come in handy. Sometimes that extra .1 seconds may be the difference between a successful cast and a dead tank. My response to that is simple: if you are consistently, or even somewhat frequently falling into that situation, it may be a sign that your throughput is far too low. In such situations, either Emergency Scan or Power Surge (see IV-i), should be available. It is by no means worth it to cripple longterm output for the sake of a rare and easily solved situation.
--------------------------------------------
II. Talent Tree
This is my recommended build.
http://www.torhead.com/skill-calc#300rfR0RdsdkczZrsk.2
Points in Power Shield, Powered Insulators, Stabilizers, Protective Field, and Muzzle Fluting can be moved around as necessary, as these points are of secondary importance. Do not take Critical Reaction or System Calibrations. These are trap talents, as alacrity is a trap stat. Don't fall into the trap, you'll regret it.
--------------------------------------------
III. Rotation
The first thing you absolutely need to understand is that the listed heat cost of an ability is not its heat cost. The effective heat of an ability is its listed cost minus the amount of heat you regenerate while using/casting it. Furthermore, any ability that has a heat cost and activates instantly frontloads its heat, which means that it can shift you into a higher heat category, and thus have a higher effective cost. An effective merc healer keeps this in mind at all times. The following are simple guidelines that should get a novice merc healer started. Follow these and you should be able to heal adequately.
Another thing to note is that being at 0 heat is extremely bad, as a good portion of merc play is ensuring that you are maximizing your regeneration, and while at 0 heat, you effectively have 0 regeneration, which is worse than even the highest heat category.
The following abilities are listed from highest priority to lowest.

1. Thermal Sensor Overrides
Use if:
Heat > 20
Critical Efficiency Buff Not Up
Use Thermal Sensor Overrides then immediately use Rapid Scan. Continue rotation as normal.

2. Vent Heat
If vent heat is off cooldown, disregard heat. Continue your rotation until you reach 84-100 heat, 84-92 being ideal, then immediately vent heat. Start casting a rapid scan while venting, as otherwise you will reach 0 heat. Continue as normal.

3. Emergency Scan
Keep this ability on cooldown. It effectively vents heat and is an instant heal. This is a very powerful ability that should be used whenever possible.

4. Supercharged Gas
Use if:
Heat > 15
While in Supercharged Gas, you can ensure that you can alternate Healing Scans and Rapid Scans. This is vastly more efficient than your standard rotation of using Rapid Scan several times for each Healing Scan.

5. Kolto Missile
Use if:
Heat < 23
Will hit 2 or more targets
Kolto Missile will be your most important heal in AoE fights. Make sure you position this carefully, this is NOT a smart heal. This should be an ability you can place almost instantaneously.

6. Healing Scan
This ability is the backbone of your rotation. The most common thing you will be doing is using Healing Scan then Rapid Scan. If there is less than a 1 second cooldown remaining on Healing Scan and it is the highest priority ability at the moment, wait until Healing Scan is ready then cast it.

7. Rapid Scan
If Critical Efficiency is active, this ability is more important than Healing Scan. Always alternate Healing Scans and Rapid Scans while in Supercharge.
This ability is the merc healer's bread and butter. In most fights this will be the heal that has done the highest proportion of your total healing.

X. Cure Mind
This ability is roughly heat neutral, so you can place it almost anywhere in your rotation, as long as you remain in the 0-40 heat category.

Ideally you should remain in the 0-40 heat category. In practice, this may not be possible, especially if your rotation is imperfect. Most mercs will inevitably have to rapid shots at some point in a fight. But mercenary healers only come close to other healers if they can continously cast, so do not use rapid shots as a crutch.
--------------------------------------------
IV. Situational Abilities
i. Power Surge
Power Surge is not necessarily an ability you should seek to keep on cooldown, as it effectively increases the heat cost of the ability it is applied to. Nevertheless, there are times when it comes in handy.

Whenever a fight opens with damage to a raid member, such as Zorn and Toth, it can be worthwhile to Power Surge your first heal, to immediately heal the damage and begin heat regeneration.

If the tank is going to die, Power Surging and then laying off on nonessential heals for a long period can be worthwhile.

Power Surging a heal immediately before a long stun or knockdown can also be useful.

ii. Kolto Shell
Kolto Shell is not an ability you use in your main rotation because Bioware is retarded and made it horrible. However, there are still times when it comes in handy.

If you are at 0 heat or going to go close to 0 heat, due to a period of no damage, you should throw a Kolto Shell on the tank. Example: The phase transition to the Terror's realm in Terror From Beyond

Throw a Kolto Shell on the tank before the fight starts.

If you have to remain mobile for a long period of time, your heat will likely fall to 0. During those times, a Kolto Shell is useful.

iii. Rapid Shots
If your heat is above 45, and you have no abilities available to change that (Supercharge, Thermal Sensor Override, Vent Heat), you should use rapid shots to make at least some small use of your time. Rapid shots can also be useful if casting an ability will drive you into a higher heat category and you have nothing available to reduce your heat. Ideally, rapid shots will not be used often. If rapid shots comprises more than 2% of your healing, you may be rotating incorrectly.

Rapid shots is also useful when remaining mobile. Do not attempt to remain mobile for long periods of time if possible, as mobile healing as a mercenary is poor, at best.
--------------------------------------------
V. Conclusion
Mercenary healing is based primarily on its ability to cast single target heals ad infinitum. Its primary mechanic is resource management. As a mercenary healer, you will use single target heals a lot. Its closest WoW analogue is the Holy Paladin. You will never be able to match the output of sorcerers and operatives. At best, you may see sustained hps of 2100. However, playing a Mercenary healer is a difficult and rewarding experience, and if you stick through it, you can say that you have mastered one of the most difficult specs available in SWTOR.