You will generally find that most sucessfull multiboxers only run 1 melee and the rest casters.
The reason being is that using /follow as the main way to move around its quite difficult to sucessfully have 2 characters in melee combat range without a problem. If you want a healer / dps in the mean time why dont you choose a Priest or a shaman to fit the other spot, both have decient casting abilities and u wont have the kind of melee combat zone range issues your having now. Both priest and shaman bring valuable buffs and both have great healing & dps abilities.