imho:
priest always need healing immersion reset glyph. too good to pass up.
also, when u r in mass pvp bg, throw power and endu buff whenever(well, u know... :D) u see group of people in range unless you are certain noone died for a while. it means ALOT.
dont fck up with plagues and ES. target people (with ES even objects/monsters) that are less likely or unable to dodge it.
kaia on cappings and when u climb over stairs with people. sleep key opponents (mostly healers, but use on other as well, depending on situation)
divine intervention wins vs doors(CS). use it. it also saves people that have overcommited to push or are under serious cc locks.
pay attention to your ally healers. two healers covering each other can stall shietload of people for crazy amounts of time.
use your melee skills to interrupt capping and to KD people(meta+staff skill combo).
also, remember to yell at your premade via TS to peel annoying people off you.
have fun.
while it is important for you to have fun, i think that you are playing the wrong class if you pursue kills with a healer aggressively. you can go for a finish if the option is there, but not if that means losing couple of your own team in the process. can you play as suicide bomber and have fun? sure! are you more useful than a healer whose slot you occupy in that raid? probably not by a long shot.