Elemental and restoration shammies are really good in arena, mostly in 5v5 though.
In lower brackets, shammies just get cc'd too easily, so if you arena on a shaman you'll probably be doing mostly 5v5.
As far as I know there's no real decent setup for an elemental shaman in 2v2, and there are only a few for 3v3.
Resto's a different story though, with a warrior or rogue pumped up on windfury, there's a lot of damage flying around, with room to heal.
I've always seen hunters as soloers, in my opinion, this persists through arena play, as they have no real synergy with other classes, besides the mana drain part. Hunters only work in setups that allow them to stay away and mana burn people, in my opinion at least. Most good hunter setups are 5v5 setups. In 2v2 and 3v3 I've generally ignored them after BW was done.
I'd roll resto shaman, simply because they can hold their own in every bracket without having to rely on cooldowns too much.
If you insist on playing enhancement, play the hunter, enhancement is the second worst talent tree for arena play imo.