As Phate pointed out, the 2's are extremely gimmicky and that's a fact. The higher the bracket the better variables in combos you have.

Before I played my Shamans though I did play 3 Fire Mages. I dabbled a little bit in the 2's and moreso in the 3's which took place in Season 1. Almost hitting a 1700 rating with 3 Fire Mages it was all about the burn and burst DPS. I did manage to get an 1800 rating on 5's though for 1 week and then fell down (reason being Frost is superior in Arenas, but just wasn't my style).

I see this goal though overall being harder to accomplish 2's. The main thing we as multi-boxers have to our advantage is focus fire, and that is huge for the mid ratings since most teams don't even seem to run an /assist train. I would suggest playing a class you love to play and let it evolve from there. I know that's open ended but that's what counts in the long run, Blizzard has done a great job making many of the classes very well balanced.