Playing this map in local coop with a friend, game crashed after killing that Santa's squirrel (was that a squirrel?).
This map has great potential! It is very funny and I think that I will play this again with this new release
My two cents:
Bosses must be more difficult, for example that squirrel is too easy, spawning lots more green slimes could be funnier!
Bosses must be in a separate rooms with stairs, 'cause of the checkpoint activation if both player dies
Turrets with mage's shoots are a good idea but they must have more HPs
Sometimes checkpoints are too near to mobs horde, maybe you can find better places to put them
All this criticism only to improve 'cause this is so far my preferred campaign (after the original one), and I'm going to try in hard-mode.
Your coop concept is really awesome
EDIT: I loved your soundtrack