With such a spell there is going to be an ideal exchange or raid comp, and it will be soon figured out and used. In the current matrix, don't underestimate ele shamans getting aoe silence from the boomkin and boomkin gets purge, which is a very strong exchange. Either way I think there shouldn't be any healing or dmg spells involved. Resto shamans getting stealth is for instance a fine one, but else it's gonna be OP as fuck.