I am a paragon level 93 Monk with Wave of Light Build. Of course, my goal is the Paragon Level 100. I have run almost four hours to test the drops and items in the Act I and Act III which both are my favorite farming spot. Lucky for me, three keywardens run all get the key drops.
Items Drops: Five Legendary Items from Act III and Three legendary items from Act I. But none of they is of value to sell in the Auction House.
Hours spent: Two hours in the Act III and two hours in the Act I.
XP Bonus: 40,000,000 in Act III and 45,000,000 XP in Act I. I guess the vast room in Act I is good for my Monk to move when come across the walled and Molten Monsters.
MF and GF: Gold Find is +475% and Magic Find is +474%.
My conclusion: Act III is good for the Demonic Essence and Items farming. Act I is better for power leveling. Items drop quality should be improved really a lot.