A quick story about a 4 player coop game from last night. We are on our second playthrough, with really decent weapons from New Haven.
We had just finished getting all the booze for Crazy Earl and zoned. We take two steps and about 5-7 little Spiderants pop up, so we lay waste to them. Another 5-7 pop up, along with some slightly tougher variants, and just as the last few are about to go down, a fresh wave pops up with even tougher spiderants (Overlords, Queens, Kings, etc). The waves are coming faster and faster now, with tougher and tougher spiderants, until there are 2 badmutha versions running around, one lighting, one acid. The damage of just ONE of these things is INSANE. I'm playing Brick, my shields are at 751, and health at 1,600+ from skills and +health mods.
Just one ground slam attack from one of these badmutha's takes all my shields and my health down to 100'ish. The attack is one hitting my friends (a hunter, soldier, and siren) if they get caught in the blast. Luckily there are still quite a few of the weaker spiderants around, so we can get second winds. From start to finish, the fight lasted around 3 minutes, but it was non-stop chaos the entire time. This game freaking rocks.
I'd suggest that people do just the main quests on the second playthrough, ignoring all the secondary quests until after you've beaten the second playthrough. At that point all the baddies get reset to level 50+, and the side missions will become a challenge again.