to the OP, You may want to learn how to play your class a little better.... I am a 664 resto druid and i can absolutely outheal disc priests when shit hits the fan... disc is only good when a majority of the damage is single target.. and even if they blanket the raid in shields, they really need a raid healer to help restore the health to damaged raid members.
All of this being said, why would someone care if a certain class was OP or not?... i have never been aware of a situation in which, outside of mythic competitive raiding, a raid consists of all "disc priests" because they are "op"....?