The paths would defeat Itachi..Mid difficulty just becasue Itachi would weasle his way out of things, but eventually, the paths would corner him. Pain has powerful attacks, whilst all of Itachi's powerful techs take a large strain on him. Visual based genjutsu will not effect the 6 paths, or at least I dont see how it would when they are all dead. And are only being controlled like puppets through chakra. And since they all attack in a group, if the genjutsu is placed, one can easily snap the other out of it. Tsukoyomi will be uneffective. Amaterasu will work on a single target, but it can be easily absorbed. The only big deal would be susanoo. But pain can hold it off for enough time to use chibaku tensei, with that, Itachi is done for.