are you high? 1.no it would not bounce back its an attack that does internat damage its NOT shinra tensei it doesnt rely on crushing power
2. tsunade wouldn't have the chance vacuum palm is faster then her and whats the point of summoning katsuyu if she ends up having to protect her
3. as for the hokage thing i honestly dont know maybe it was just cause of the plot
4. katsuyu wouldn't be given the chance to split once she's summoned vacuum palm would mess with her chakra system
5. dude rotation takes care of the acid and why are you denying the obvious
the obvious being by the way that katsuyu is NOT indestructible just highly durable and all the attacks she's taken have been the opposite of gentle fist attacks like vacuum palm that aim to do internal damage to the chkara network. i.e you have chakra then gentle fist attacks screw you as soon as they hit
and where did that weird bounce back idea come from anyway??? if it was normal taijutsu sure but this is GENTLE FIST'S VACUUM PALM google it sometime
1. i am not high.
2.And Katsuyu is a defensive and offensive summon so thats the point to summon her, Hiashi cannot Do anything to katsuyu as she can Split apart at the point of contact, not because she is a slug it automatically means she is slow.Look at her size compared to hiashi, And tell me how can he hit her nervous system. HUH???
3.Katsuyu would have time to split apart as she can split apart on contact, even if he hits one of her clones, she can simply dissipate that clone and Continue without harm.Also he would not Be able to hit her Nervous system as she is so large
4.How the Hell can Rotation take care of corrosive acid, Her acid is strong enough to melt rocks,what will he do Spin all the time. Well no he cant.One touch of her acid can kill him as it is deadly.
5.And her body is slimy and rubbery seeing as she is a slug. You think that Hiashi can Even hit her judging from her size which is comparable to a tailed beast???
6. When Hiashi approaches Tsunade, her dodging abilities will come into place and as soon as he tries to hit her, she can hit him behind his neck and disrupt his nervous system points. And she can also Punch him if he touches her, and she can also grab him and swing him high into the air. you act as if Tsunade will stand there and Take hits from hiashi, dont you think she knows all his abilities, seeing as she is the hokage and everything. She is the best medical ninja,and is therefore skilled in the art of evasion.