Damage Dealers:
- Your healing no longer benefits from PvP Power
- Your damage still benefits from PvP Power
Healers:
- Your healing still benefits from PvP Power
- Your damage no longer benefits from PvP Power
- You will notice in your character tab that the percentage your healing is increased by PvP Power is half of what is was before 5.1 dropped. This is only a tooltip fix and your healing has not been affected by this. This tooltip fix reflects a change made right around MoP release that cut the benefit of PvP Power for healers in half simply because PvP Power was too good for them.
Healers and Damage Dealers:
-With Patch 5.1 a global healing reduction of 15% has been applied. It's called Battle Fatigue and can be found in the general tab of your spellbook. The 15% healing reduction occurs after having damaged or received damage from an opposing player and if you are out in the world it should not be active if you are not currently in combat with another player. I have not yet had a chance to test whether this global healing reduction is always active in Arenas or Battlegrounds or when just in combat when in them. I would assume the later, but can't definitively say.
Conclusion:
-Damage dealers your healing has been nerfed twice, once due to PvP Power no longer affecting it and once due to the 15% global reduction. Your damage remains the same.
-Healers your healing has been nerfed once due to the 15% global reduction. Your damage has been nerfed once due to PvP Power no longer affecting it.