How to get Inferno Machine efficiently in Act 2?
Vault of the Assassins is the best way to 5 stacks. Port to Desolate Sands and start looking for the vault, killing any elites on the way. The best part of the vault is that you get a checkpoint once you enter it, so if you don't get the key from the keywarden, you can just resume game and you'll start in the vault. The Oasis has many packs, so you can definitely TP out with 4 stacks and easily find another pack in the Oasis.
This keywarden isn't too bad, but if you stun him while he's down his spinning attack, he will not stop his attack. He'll continue to damage you while he's frozen. He also has vortex and teleport, so CM wizards can save their teleport to escape instead of using it to get close to him again. Getting an empowered shrine right before the fight lets me facetank him straight up.