Since the boss is level 75, level up your party members to 78. It's the most time-effective thing you can do. That single level will do wonders.
I don't remember having any noticeable problems in that fight except for retarded AI characters trying to take a bath in the ether, but by that time I had spent a lot of time crafting gems, my characters had many affinity coins, at least one extra skill tree, and I was beginning to figure out how to put those pieces together in an effective way.
Last edited by Player2 - on 07 February 2018