Awsome map, me and two friends finished it, but the last boss was troublesome with his insta gibbing aoe ability, i'd suggest making the protective bubble more visible and bigger, or giving the players more time to run into it.
We managed to defeat him by pausing the game whenever he used arcane destruction and look for the bubble, and if we survived it we saved the game and could retry if we died.
Also when you save and load in another game, you lose stats, but not from the items, our items stats were higher than the ones we had when we saved, but we still lost stats somehow.
Lower the health of the iron golem boss, he's easy but boring because of his high health.
I would also suggest adding a rogue-like class, or a skill (agility) class.
One last thing, there is a bug with the sea queens tornadoes, if a barbarian push her to the edge, he can be pulled outside of the arena by the tornadoes.
P.S played about 11 Hours and for a beta map, that's pretty much.