Quote Originally Posted by accretion
I currently 2-box a BM Hunter and Disc Priest and it's a terrific all-around combination. With a high-aggro pet (e.g. bird with screech) you can even duo most instances.
I'll second this, doing the same thing, albeit with more focus on the Holy tree. Can brute force duo most instances and elite group quests.

It is _much_ easier with a screecher pet (+PoM), just stay off the multishot button a few seconds and you are golden, the pet will easily keep aggro on multiple mobs.