really first of all kakashi has improved a lot since pain fight
secondly deva path needed another path to take on kakashi who died because of saving chogi and chakra exhaustion
and let me make it clear a<b<c logic don t work in naruto
well kakashi needed choji and his dad for his plan
deva path is stronger than kakashi and i know he died just to save choji but you have to keep in mind that the deva was just toying around ...
i mean when when kakashi was on earth pain was able to go and finish him with a blade also we wasn't going to need the aura path to help him if kakashi wasn't using choji and his dad
i know that kakashi become much stronger
and for the tailed beasts they are nothing compared to kyuubi
prove that BM naruto defeated them without problems
so kyuubi is stronger than the 5 other bijuus together
kakashi only managed to hold two of them not even win against them
kakashi will hold his own in the battle but he loses