2v2 is going to be, imo, an incredibly frustrating experience to try and multibox. You really don't see too many MBers do 2v2 or 3v3 (seriously, not lose 10 games a week kinda thing) because the real power comes from massive burst damage on focused targets in 5s. The only class right now that can do that is ret pallies (while being immune), so maybe 2 ret pallies will work but who knows at 80.

Druids were OP pre 3.0 because they could form shift and get away from focus fire, they could cyclone someone, pillar hump, HOT up, innervate, etc. All that is exceedingly difficult if you are multiboxing, while keeping the 2nd toon busy on someone.

Beyond 2 ret pallies its really hard to think of a 2v2 combo that would not lose most of its games, I run my shamans sometimes in 2v2 and its just laughably sad - one pretty much gets feared/stunlocked/DCd/cycloned/hamstringed/silenced/etc, the other one dies, and its gg.