Im running the Priest + Lock x4 combo with similar intentions as you. Although I've never done Heroics, so Im not sure about using this team for that.

So far leveling has been a breeze. Void Walkers make great tanks so far (not sure about later levels), my DPS is insane, and my priest does nothing but Heal-On-Demand.

I am going for Tailoring/Enchanting as well with one alt in Skinning for $$$. Havent tested PVP yet in BGs, although I did pick-up my first ever, and so far only, world PVP kill the other day
Been running instances for leveling and havent run into any issues with this team that cant be resolved with a little tweak in strategy. Gnomeregan was a bitch, but i dont think that had anything to do with my teams make-up.

Good luck with whichever team you decide on.