I'm going to lvl up a char that probably will be 85 at 4.1.0, which one should I choose, considering 4.1.0 patch changes and that my main goal is 2vs2 arena?
Atm I got Shaman at lvl 45 (resto at 85), Rogue at 23 (Subtely at 85), Pala at 83 (Holy or Ret at 85) , Priest at 81 (Shadow or Disci at 85) and Hunt at 21 (BM or MM at 85).
Well Ret Pallies are getting a nerf next patch, but I still think I will play mine even afterwards. Really hard to tell you what class to play. Really kind of depends on what play style you like.
All those classes you mentioned will be fine in 4.1. Paladins will probably struggle though and Shadowpriests probably too.
However, rolling FotM will never get you anywhere. Also playing a Rogue or Shaman is vastly different and requires a different skill-set. Success isn't that much a matter of class as it is skill. (which says a lot about Cataclysms balance).