Let me get this straight: Oro (full health) vs Kabutomaru (which is basically Oro again). Both can use full abilities including edo tensei.
Thats an incredibly unbalanced fight, with the conditions favoring Kabuto. Even though Oro has full health, Kabutomaru is essentially Orochimaru with whatever Kabuto knows. PLUS Kabuto has WAY more edo zombies at his disposal (at least more fearful ones), even if Oro has the previous hokages. This is especially unfair when you consider this: Edo zombies cant die unless their sealed or are no longer tied to the impure world. Kabuto has Chio. If Kabuto dies, Chio brings him back with her revival thingy. Chio comes back too. Repeat.