For a pvp team, I'd recommend something which is capable of running (PvE) Heroics.
Because gearing up for PvP, with badges (PvE) reward... is faster then grinding battlegrounds.

Shammies are an excellent option for PvP.
They can stagger Tremor Totems for fear protection.
Have a ton of other totems for configurable buffs.
Put out high controlled burst.
Wear mail armor and carry shields.
Can heal, in their DPS form.
Possibly consider 1x Feral Druid + 4x Elemental Shaman.... and dual-spec the Druid to Balance for PvP (don't bother with any healing from this toon, stay in Boomkin the whole time... manage Eclipse if you want, or approximate it with a castrandom).

The latest flavor of the month team...
And they've been around much longer then the month.
Is: 1x Death Knight (Frost/Blood), with 4x Retribution Paladins.
The team gains passive heals from Divine Storm and Judgement of Light.
And through Art of War, can toss about frequent heals either to each toon individually or targeted at whoever is taking damage.
The team can clear all 5-man heroics, and is a beast in PvP.

I'm in the process of leveling 5x Feral Druids.
With 3x Cat, 1x Bear and 1x Tree, the team will be able to do any heroic.
5x Feral is untested/unproven for high end pvp, but they have a massive number of toys/tools to play with.

There are a ton of options.
I've also got 4x Affliction Warlocks + 1x Discipline Priest.
I don't see heroics as an option for this team, but it is a PvP focused team.

I could see a rogue team doing quite well.
Possibly include one or two druids for heals.
If you went 3x Rogue, 1x Feral, 1x Resto, you could do heroics.
And then have either 2x Feral, 3x Rogues for pure melee.
Or some combination of healers with the rogues.
You get two battle rez's, and some heal options too.