Mozared wrote:
As a healing priest, the duration of the fight doesn't depend on you at all. Which basically means that in a specific fight, the tank will always take X damage; you need to keep your mana and mana regeneration high enough to be able to heal that X damage. The only thing haste changes is the way you deliver it; with a 0,5 second haste you have some more room for mistakes.
Casting faster does not mean you'll go OOM faster since as a healer you will not suddenly be casting *more* heals.
For a shadow priest, your statement is right; it's just that shadowpriests should generally have enough mana regeneration tricks up their sleeve to counter the increase of the total amount of spells cast (due to haste).
That's not entirely true. When healing, you take into account different variables and have to make an on the spot decision. Haste, or quicker cast times, can alter that decision process.
You take into account things like:
What moves the mob has.
How much damage your tank is taking per hit.
How much damage your tank is taking from special attacks/situations.
How much your heals actually heal for.
How long each cast is.
Now let's take the Hall of Lightning. The first boss is a warrior, who stance dances. He jumps from defensive, to battle, to berserker stance, in any given order and random times.
When he jumps into Berserker stance your tank can take loads of damage in a short amount of time. So your decision making has to be that much quicker.
If you had no haste, you may decide that you won't be able to keep up with damage using heals alone so you bubble the tank, cast PoM, Renew, then 2 flash heal when the bubble breaks.
Now with haste involved, you may decide that you can keep up with the heals because your casts are coming faster. So you , renew, PoM then spam two greater heals instead of shielding...
Now forgive me for this part, I'm at work, so I am going off of base mana for a level 80 priest is 3863, according to wowwiki. And am not using any talents that reduce mana(don't have the time for that math sorry).
In scenario one, without haste, the healer casts PW:S for 889 mana, then hit the tank with a renew for 657 mana, then a PoM for 580 mana, and finally 2 flash heals heal for 696 mana each. All together that cost the healer 3518 mana.
With haste, you cast renew for 657, PoM for 580, and 2 greater heals for 1237 each. To make a total of 3711.
So in the end, the same amount of damage was taken by the tank. But because your decision process was different, it made you cast differently and cost more mana (albeit not much more, but still more). This is just a simple scenario. You could take it even farther and include variables like the Five Second Rule. Would the bubble from the "No Haste" have kept the damage off the tank long enough for the healer to regain mana at the OOFSR rate? Possibly.