Resto Shaman pvp

Hi. It's my first time playing wotlk and I've some doubts.
I'll play pvp (mostly arenas) with some friends and I don't know wich class choose.
I am main resto shaman since cataclysm. But I watched videos of wotlk and it looks quite different.

Is resto shaman competitive? (arena) I mean, knowing how to use the shaman will I have problems?
for example a rshaman/hunter , rsham/spriest, rshaman/shi.t... can win against a disc/hunter, warr/holy, rogue/disci...(2.2k+)? Or it's only viable with warr/rshaman, alock /rshaman ...