Priests are a fun team to mess around with in AV/WG, but they lack the utility that makes Shamans great in smaller scale and Arenas. HolyNova is fantastic for keeping your health up on the move, but it's not going to kill people in arena. DoT's are easily dispelled and don't do enough burst to really challenge a decent healer. The point, I think, of playing Priests is for mobility. Most of that mobility is negated by the fact that your real DPS spells are either channeled or have a 1.5+ second cast time. Since you're going to have to stop and cast to kill people (unless they're PvE geared, have no dispel, no cooldowns available and no healer), I just didn't see the point of not sticking with Shamans and the totem utility.

On a brighter note.. what I ended up doing with my priests is turning them into a mobile healing turret. I spec'd them all holy and, when I'm bored enough to log them in, spend most WG's running around spamming RoundRobin-ed CircleOfHealing, ImpRenew and PoM on my raid. You will never get so many positive comments as a multiboxer as you do when you multibox a pure support group in AV/WG