be nice if bosses would retain damages if you go in with another team just like opponents in war.
I humbly disagree. Each time it comes around I do better. It is meant to be a challenge I think. Something to see how much you grow, and how well you have figured out how to chose the teams wisely. It would make it worthless as a challenge if you could just keep hitting the bosses. Not a challenge at all.
Sorry. But good luck! You will do better as you grow stronger!