I just started dual boxing about a week ago and from my experience so far it is very difficult to win arenas. I have been trying a few skirmish arena matches every time my characters (rogue+druid) are at the level ranges of 18-19, 28-29, 30-39... etc. And what I have found is its not as easy as you might imagine. Now granted I am using two different classes so it is much more difficult, but still I cannot imagine that you would be able to dual box shamans in 2v2 above 1700 rating. Its simply to hard all they have to do is lock down one of your shamans and its game over.