When I firsted started dual boxing I used a hunter and a priest and leveled it up to level 60 very fast and very easy then I started using 3 boxing between my preist hunter and lock very easy combo in my opinion

My second set was a set of casters 2 mages and a lock very easy as well to use

But if you are dual boxing I would recommend using a main hunter with a tanking pet and then a pocket healer that can also do some good damage to help out. :thumbsup: