No one have mentioned any of these points before, so here goes:

1. Don't forget buff removal (Han, or Wind main's Wind Dust Mystery if you're poor like I was when I was doing it ages ago). The reason why The Final Trial is so hard is because the Pains buff the crap outta each other, you remove all those buffs, and they hit like little girls.

2. Clone tanking: Have clones tank all the dmgs by having ninjas that makes clone and ninjas that can shield them. Back when I was doing Final Trial, I used Wind main, Sage Naruto, Iruka, and Gaara.

3. Prioritize and focus dmg. Don't just aimlessly atk them, kill them one by one in order of importance. Interrupt/cc whenever need be.

It's a bit outdated with the changes we've had since, it didn't work for me at all while I was around that level and BP.