Doing AB more as a guild will make it better. But your teammates still need heals.
As for PvP gear:
I don't have any PvP gear from the PvP reward system. I do have a hand ful of +healing and +healing\damage gear. I can get my healing upto +500 (just over) with gear such as Robes of the Exhaulted (Baron), gear from Silithus quest rewards, and some random drops. Of course I loose nearly 3k in mana to wear it. Gotta love priest itemization.
The PvP reward gear is good for pvp, lots of stamina, fair intellect adds and good + healing\damge adds.