It doesn't protect the user from genjutsu, but sasuke is pretty immune to genjutsu.
I think you would have to get sasuke under a genjutsu even for a second, that way his chakra would be disrupted and susano'o would disappear until sasuke breaks out (enough time to attack him)
I think you would have to get sasuke under a genjutsu even for a second, that way his chakra would be disrupted and susano'o would disappear until sasuke breaks out (enough time to attack him)