Think about it like this... If Sasuke could beat Kabuto by himself, then him and Itachi would've captured him easily. None of they're attacks worked until Itachi pulled out izanami. A jutsu not even Sasuke knew about. That sound genjutsu that Kabuto used on them, if they didn't put genjutsu on each other, they would've been done for. Sasuke can't put genjutsu on himself now can he...