Mage is extremely viable even with garbage teams. Just depends on play style and spec that you play. Fire is extremely viable, and if you have enough crit you can do insane burst, especially with zerker. Personally, I'm loving lock rn @ 29. I play either affliction or demonolgy. With affliction I can tear apart mid fights w/ a good healer and as demo I can throw out large burst. Either classes are viable and are most definitely not considered fotms