I'd say with the right gear - monk is best. I doubt DB will be kiting any time soon, so that locks out the ranged classes since they rely on it.
Monk and Barb rely on being able to survive taking hits - so imo they will do best in the long run. Personally, I decided to go with monk for botting since they should stack dex + resistance in order to survive (which also boosts their dps), while barbs should stack on vit and resistance, but that doesn't really help their dmg.
While writing this, I have little to no knowledge about monks taking in inferno after act 2. But my friend barb is tanking act 3 inferno like it was act 1 or 2, he just has to move out of desecration, molten etc and he's not gonna die - ever.