I did it for the first time today, MP4 with a friend. We ran 6 times and I got 4 organs, made 1 ring with crit, good str ofcourse, but dex and life% instead of vit. Also the crit was only 4.5 and no attack speed so it doesn't add much to my char, it even gives me 700dps less and slower attack speed, so less fury regen.
Gonna try it again later with someone who has more dmg output (~200k dps) and on mp6.
My own dps with Battle Rage and WOTB is ~130k dps, 46% crit chance and 1.99 attack speed, dual wield.
The axe gives me 10% crit through the weaponmaster passive. I feel this gives me higher dps (real dps, not only in character screen) than the higher weapon damage from the mighty weapon would give me with HotA, and also helps keeping up WotB via battle rage rune.
So far it seems that mp 5 or 6 should be a good place to start for me. Would like to hear from barbs who have tried mp8 (or higher), is that a huge step up from mp6?