Make sure you have your units on 100% crit chance except for your healer. 

** / A.Ras / Kitty Clarisa / Tammarine is the team to go with. 

Phase 1: Focus down the boss ( purple), reset if no defense break procs

Phase 2: Kill the ads so Aramintha's Immunity goes away. 

The reason you need 100CC is because the ads can only receive damage from crit hits, so you MUST use CC to minimize the RNG in the floor. 
Important to note: non-attack skills are punished by burns (cannot be resisted)

Good luck!