People are saying that since Shikamaru is smart, he will be the first target. Sure he will. But he's smart enough to realize that, and won't put himself in the position to end up being the first one killed. So here is how I see it going from then:
Shino's bugs can be sent UNDER Susano'o and begin sucking Sasuke's chakra. Maybe Sasuke's lightning can kill them, but Shino's bugs are so many that they will always be coming back.
Shikamaru's Shadow will continuously force Sasuke to move, which would make it impossible for him to form a full Susano'o.
Being unable to form a full Susano'o, he is also then open to ariel attacks from Sai and taijutsu attacks from Lee, who is too fast to get caught by Amaterasu. He would also have to avoid all of Ten Ten's weapons as well.
Sure he could probably take out a few with Amaterasu, but right there there is a scenario in which he could lose, and Choji, Sakura, Hinata, Neji, Ino, and Kiba weren't even mentioned. How does Sasuke counter this?