I find desertation(soul skill that reduce multi hit) works super well with boss, considering that you have enough burst to either 1 or 2 shot the whole rage period. Since the skill hit almost 100% the times, it means no longer u ahve to worry about random unlucky stuff multi hit from both mob and boss.
Then the session is easy to play. I run a 3 water + ramirel and able clear it quite comfortably at 20k atk(self+friend garuda)