Originally Posted by
Kalisandra
The problem Resto has it that while it has lots of great utility for m+ and PvP (not so much in raids), it's cooldowns were nerfed in strength, and it takes a fair bit of skill to use the utility right. Thus while Resto is still very strong in the hands of great players, for most players it's not that great, and they find going to a class that simply has more raw throughput gives them better results.
It doesn't help that in raids, Resto's mastery generally doesn't do a damned thing unless all the other healers are dead, and it's not strong enough (especially as most players will gear away from it) to save the raid at that point unless the fight is almost over. It is nice when you can do that, of course, but usually it doesn't work - not least because by the time the other healers are all dead, most of the DPS is too, so you're getting chased by adds, fire, and all that, and mobile healing isn't a Shaman's strongest point (hope you saved Spiritwalker's Grace).