I should mention I'm running a Druid tank with the team. The Druid has only recently started doing BGs with the shaman, but that's just because of the 85-89 bracket I'm doing AV for leveling. I've made the decision to just run 4 in BGs (other than leveling) as I feel 5 is too many toons at once. Obviously for 40 man BGs it doesn't matter, but 4 toons is the absolute max for 10 mans, and I would argue that for 15 mans 5 toons in one spot is too much.

Not that it matters, but 4 enhancement shamans is the first time I could actually win in WSG. I could carry the flag and stay alive with massive healing support from my toons, or I could assault their flag carrier with some ease once popping cooldowns. Really the only class I have trouble with is resto Druids, but I think it's because I'm not effectively using purge. Once I get ascendance I will likely save it for those pesky druids.

More rambling: originally I thought I'd run my Druid as resto with the shamans. However, so far I haven't needed healing support in BGs. Arena will be different, and I may try to heal my own toons, but I'm guessing I'd be more successful with a solo healer.