Priest Healing Aggro Tactics
This discussion on healing aggro is based on numerous controlled tests (as controlled as possible). In brief, it can be concluded that healing aggro is based on hp healed and generates approximately 65% of the aggro per hp that is generated from damage. Subtlety will reduce this to 50-55%. Over-healing has no effect on aggro, since aggro is based on actual hp healed. Aggro is applied to all mobs that your healing target has aggro on, ones that know of your target, not necessarily every mob in the area. In addition, aggro does not dissipate over time, at least not a short period (a few minutes).
Contrary to popular belief, all your healing spells (Lesser Heal, Heal, Greater Heal, Flash Heal, and Prayer of Healing) generate the same amount of aggro per hp healed. This means that one Greater Heal is like using 3 Flash Heals to heal the same amount, or one Prayer of Healing on 4 targets would be the same as Flash Healing each of them. PW:S generates about half the aggro of an equivalent heal (i.e. your 950 point shield is about the same aggro as a 475 point heal). Renew will work the same as a regular Heal, except the aggro is generated over time, so it works like casting a very small heal, each tick.
Also, increased distance from the mobs reduces the amount of aggro drawn from healing/damage spells by a small amount. So, when you can, try to stand back from the fight, while still remaining within range of your healing spells.
Fade:
Fade seems to reduce aggro by about the equivalent of 2-3 Flash Heals. The aggro returns when Fade ends, however it appears to only return after you act in a way that increases aggro again, so, let us say you have 3000 points of aggro, you Fade and it reduces it to 1000, the mob goes back to the tank. Fade then ends and you will stay at 1000 as long as you do nothing. Once you cast a heal that generates aggro (say 500) you will get that additional aggro, PLUS the amount Fade had reduced, so you’d jump up to 3500. This may be a bug, I don’t know. Also note, if you have too much aggro, and Fade is insufficient to remove enough aggro to make the mob turn from you, then it removes nothing. Fade appears to be all or nothing; if it fails you have reduced nothing and have not made it any easier for the tank to pull the mob off of you than if you had never activated Fade in the first place.
The timing of using Fade is very important. If you use it too early, it will be wasted, and you will not have it available when you need it. If you use it too late, you will not be alive to use it. Therefore try to use Fade only when a mob running at you or shooting at you. Activating Fade before you have aggro will not do much, if anything at all. The best situation is to activate Fade when a mob is attacking you, and then stand there as he turns away. Do not heal yourself right away, or shield, or anything, give your backup healer a chance to heal you, and your tanks a chance to build more aggro on the mob before Fade ends.
Other than having Subtlety, the best ways to avoid drawing healing aggro is obviously to not heal too soon in a fight, or too often. The problem is, you often have no choice, you can either chain heal, or let the person die. In raid zones, alternating healing with a backup or secondary healer may be necessary.
