When I was finally able to beat it I was a wind main and used guy, sai and Neji the wind main had dance of impertus and spammed clones the formation was

*x *x *x
*x Neji *x
Guy Main Sai
I was at level 77 with 24k power
I found that strat on another thread and oddly enough it worked. To add insult to injury after all my efforts alone no one died when I used this strat. So if you have access to wind you can give this a shot and see if it helps. Some people can't pass that one with full marks until level 80. So basically if everyone constantly dies now try waiting a bit until you're stronger or settle for beating the chapter with out the sealed for now and come back to it later on. Other then that can't help Normally it helps to mix and match to try different things and that's what Kakashi's shadow clone is for to help you test out new formations for the best possible results. I've been using the clone a lot lately. Well take care and good luck.