*ONLY THE HOST GETS THE TROPHY*
This is actually easy since unlike the first game, it can be done in co-op. Just stay as a team and it will be cake.
Or if you are level 30+ you can do it solo. Once you're level 50+ this mode becomes too easy. I'm level 140 and can beat the bosses within 2 minutes, so if you're stuck, level up more and then go back.