So you guys start the quest that has you go in the VoA? Doesn't it bork up the checkpoint otherwise? I tried it once and it put me back in town or somewhere random when I reloaded. (I load the kill Kulle quest when I start farming)
You actually can load up the last quest to kill Belial. There's a few spots you can go to to build up your stacks:
Sewers
Black Canyon Mines(immediate area around there)
Road to Alcarnus - Immediate area for a potential goblin and then the first level on the way to Magdha. No champs on second area so don't bother
Ancient Path just for the potential goblin
Then find the Vault in Desolate Sands which can be a bit of a pain, but once you find it and finish it, the next time you start the game you'll be inside it. Use the portal to mark it on the
map and then go back to town and repeat the cycle but only use waypoints because that way you can take that portal back to the Vault saving more time. It's a great run.