I was trying the survival mode with 3 friends and several different combinations (All paladin, 2 paladins, 2 warlocks, etc.).
The only method that would work is having 3 paladins play until the lich is going to spawn, then have one ranger enter, buy all his damage upgrades and finish the lich. This seems like cheating to me, so I'd like to know if there is an actual working combination.