PvE:
WW - seems a bit underwhelming, the damage is okay but they have little to no utility. Probably fine in 25man, but not too great in 10man, especially since melee is meh to begin with on most PvE fights.
BrM - Very strong from what I can tell. Our BrM takes a significant amount of damage, I feel it's more than our other tanks, but he also seems easier to heal for some reason. Overall, I think they're quite good.
MW - Strong. Very strong. Some of the best healing I've seen with infinite mana, we have one in our 10man and his healing is really really good.
PvP:
WW - BGs and 2v2 they're gods. Really strong, their self healing is incredible and their damage is very high. In 3v3 they're awful, they die incredibly fast if they're focused and they can't stay on targets long enough to do anything. If you pop Tigerseye Brew and you'll just get stunned/disarmed by any good team and do nothing during it, and without Tigerseye Brew stacks you do no damage. I haven't done 5s on my Monk, guessing they're bad there, but honestly 5s is nuts so really anything is possible. The right comps could definitely work with a WW for sure.
BrM - They can't PvP. Don't play a tank class in PvP, if you do, you're the worst.
MW - Very strong. Probably one of the top 3 healers in arenas, and since their AoE healing is strong I'm guessing they're good in RBGs. They do a seriously silly amount of healing though, and they're the hardest healer to kill right now. That being said, not many people play them and their PvP healing is probably the hardest healing in the game. They're by far the strongest 5v5 healer though, and one of the top 3 healers in 3v3.