for me, all MP5

farmin item + key + level grindin

Act 1 Cementry -> Festering wood -> Key
Act 2 Black Canyon -> Desolated Sand (VoA) -> Key
Act 3 Keep 1-3 -> Key

repeat...

if that act no drop key, repeat the act until get then move on next act, but sumtime damn dulan 3x/4x no get key, then try other act then go back to previous no key act..