One of the surprising and delightful benefits of having forums here is that occasionally a new member writes a very elegant piece. In our quite epic thread discussing stamina vs avoidance gearing in Cataclysm, member Adrift contributed the below on the healing model in Cataclysm:
I’ll try to provide a tank healing model for Cata, this can’t really be confirmed until raid content is in full swing so take it with a grain of salt.
The model for almost all healers tank healing will be to spam their efficient heal (and with druids and priests, rolling a free hot) until they can’t keep up with damage. At which point they will throw out a big, mana inefficient heal, ideally at the point where there is minimal overheal. This is basically a max HPM (heal per mana) model, and to be used on steady tank damage.
With low avoidance, you will decrease the ratio of efficient to inefficient heals, that is, the healer will need to use more mana over some period of time. With more stamina, the healer will have more more time to judge the max effectiveness of an inefficient heal. With high avoidance and low stamina, any bad avoidance string will be very urgent.
From a healer point of view then, I would like my tank to have enough avoidance so that I can spam my efficient heal to ideally keep the tank topped up, but more realistically, keep a steady rate of decrease in his health such that I don’t need to use my inefficient heal too much (“too much” is unknown until I can get a good feel for healer mana). At which point I will always prefer stam to give me max reaction time and time to judge max efficiency of my inefficient heal.
Burst periods are usually predictable. There is no reactive healing at all during this time. You’re either spamming or given experience you’re able to predict the damage incoming and I’m throwing the appropriate heal out regardless of a hit being avoided or not, after all I can’t predict when a tank will avoid a hit. Basically, I’m going after a hps model where I’m trying to match as closely as possible the dps the boss is putting out.
This all assumes I’m only healing the tank. If there is a burst of heavy AOE (<50%) of a raid member’s health, then at least 3 out of 10 casts following it consist of a heal on raid. At this point avoided hits will give me time to catch up. But stam will do the same, at a higher cost in mana. The difference is that if the hits aren’t avoided, the tank with lower stam will require more urgency.
Gearing for early expansion as a healer will always be for max longevity. There was a post on EJ explaining this concept during Ulduar in the priest forum. That a fight can not be designed such that with the appropriate number of healers, the HPS demands cannot be met (other than mistakes on mechanics). What longetivity gives a healer, in addition to not going oom, is less concern on their efficiency. The dps is slower, tanks are hit harder, mechanics aren’t well practiced yet, the fight is inevitably longer than it would be with experience and gear. As well, mistakes will be made such that I will have to cast more inefficient heals than I would like to. There are of course exceptions, such as mechanics where random burst raid damage is very high.
The above point is moot in the Cata model because we actually gear for throughput inorder to max longevity, with the exception of gems. Early on it will be int/spirit. Hardmodes of first tier and beyond, int/mastery or int/haste.
The typical gearing priority, will be int > spirit > haste > crit. The rationale is that I want the HPS of my efficient heal to be high so I can use my inefficient heal less. This will also mean I have enough throughput to deal with burst periods. I didn’t include mastery in the above as its class depedent where it will land. For pallies and priests I’m pretty sure it will be above haste in priority.
But the gist of all this for tanks is that I prefer a (currently unknown) baseline for avoidance, at which point I’ll prefer EH.