I'm having tons of fun at MP2 with my rapid fire farming build. I don't loot anything apart essences, tomes and legendaries (it's strange but i drop a lot it seems, maybe the paragon levels are starting to kick in).
Maybe not the most efficient way to level up, i don't have hellfire and only the gem, but to me it seems everything is just going faster.
EDIT: act1 for life! now that i can farm it, everything is automagically better
---------- Post added 2013-05-14 at 07:22 AM ----------
Maybe not optimal again, but i like the idea of spreading devastation around XD