I know some people are taking issue with the Circle of Slaughter type battles. But I have to say, I really enjoyed them this time in BL3. In Borderlands 2 I found them to be rather boring.
So far I have only solo’d them with FL4K. But I am looking forward to playing them with a full group. I think they will be the funnest part of teaming up. Slaughterstar 3000 or whatever its called verses all Maliwan enemy types was a ball. It reminded me of the original first Horde Mode from Gears of War. Hold your ground, kill what you can, find cover, move, find ammo, wash rinse repeat. Just all out fun. The final wave with the two giant mechs was awesome.
And the final round of the Creatures Circle of Slaughter on Promethea. Gearbox if you are listening, NEVER CHANGE, NEVER ALTER, THE FINAL ROUND. It is perfect as is. You end up with like 10 of the Bloated Rakks just dumping money all over the place. Difficult fight worthy of the cash rewards.