It also depends if you group PvP alot. A Warlock/Bard is definetly a good build for group PvP, since Bard can buff and deal arena damage without selecting a target.( With my 110 bard on private server I just ran into a group of enemy's and killed 3 of the 4 xD )
So you don't have any kind of heal -> just use vampire skills alot and use de-buffs or even vigor grains
I quess the tactic for PvP would be :
vampire touch/kiss -> stun -> de-buffs -> sleep -> bard attacks =) Good Luck
