It's just the Murder Circus mission from the base game but now you get to do it over and over. Unlocking weapons and perks as you go. Also there's 4 characters to play as and all of them can go up to level 9.

I mean maybe it's fun if you really liked that one mission, but this felt really unnecessary. Like I got one character to level 4, got tired of doing the same shit over and over, and gave up.

I'm fine with this ruining me getting every achievement tbh. If it sucks, it sucks. Just a shame the first DLC story and this one weren't great given how much I loved the base game.