how do you defeat yourself at toward the end of the game when you become mind controlled?

Question: how do you defeat yourself at toward the end of the game when you become mind controlled? The freaking greater heal ability is ridiculous. Its used like every other round doing about 4000 points of healing and I can only put out at most 1500 points of damage every round with my companions. I'm not making any progress.
Is there a secret to this fight that I'm just missing or did I arrive at the fight a little premature, before my companions were strong enough to do this fight? Any help would be greatly appreciated, I'm pulling my hair out here.
Answer: Ya I Feel the same thing and Same presser. I was hitting the Clone with everything i have got. i used too many sprite potion to recharge the Players. but I Use Multi Shot(50) With Each Player randomly to check my luck And i Saw Another Thing is Getting Hits. So After that i Target Both Of them With 2 Player each. After Few Hit I Get the Result.