I assume you're still doing the exp grind? Tagging with the shaman and burning the mobs down with the mages?

As for PvP, I am not a PvPer but I am guessing that the most useful add-on for you would be some sort of targeting mod. Having a couple of enemies run into your group must make for a targeting nightmare. You should also strongly consider working on the various reputations in Outland as your characters get into the 58+ range. I believe that at Honored rep, nearly all of the factions have one or two pieces of level 70 starter PvP gear tailored to each class. Honored rep should be do-able just from quests, and the gear will help you to avoid being one/two-shot by AE attacks.