I dont see how 35 lvl maxed character can have problems even with a bit bugged boss;P I also had this issue with few bosses but most likely what i did was dodge,jump next to him --> split arrows --> sayonara. This is such a cheat;/
Also for Laiken's pet,use shield that u aquired to be "protected" in hall of echoes and suddenly their damage will fall down.
That's just it, i did, and she was the only one doing massive damage. The memory-eaters or whatever and other bosses were tame roaches, except Laiken's Rumpy-Pumpy.