Okay, I don't know why you'd want to roll a healer too. If I knew there was always going to be a healer on my team that I could count on, I would strongly consider rolling dps or tank. In my opinion, you usually only need one healer sitting with the fc. It's usually better to send the other healer(s) out with the offense to give them a chance of staying alive. So, if you're thinking you guys are going to run flags together, you really might consider rolling something other than heals. As a disc priest myself, I'd rather have a dps sitting by my side any time than another healer.
If you are set on rolling a healer, I would say paladin. Paladin and shaman are about equal and it mostly comes down to personal playstyle. Shaman have no cc and no instant heal. Paladin can get a bit more armor and they can heal others to heal themselves. To me, the big difference is the races you can be on alliance side (don't know which faction you guys are playing). I love /waggle, but GotN doesn't help anything in pvp at our lvl. And stoneform is kind of lacking in my opinion when compared to EMFH.