Blood: is fine, tanks are very balanced right now with the exception of bear druids which are OP as fuck. Still the tank most focused on "healing back up after damage" which makes it kinda weird.
Frost: very good single target and aoe damage, no real utility to raid, in other words great DPS with nothing else.
Unholy: Great DPS if you have the right legendaries, "normal" otherwise, better utility in raids than frost due to at least death grips but feel like I'm forgetting another utility.