Hashirama has never face it.
So there is no really a reason for Sasuke to be scared of Hashirama, the advantage is on his side, and Jugo would going to sacrifice his life for him.
Orochimaru could force the rest of the Hokages to fight him.
In this small room Sasuke can easily burn anything and everything in an instant.
Hashirama wasn't really a threat for him and Orochimaru.
So there is no really a reason for Sasuke to be scared of Hashirama, the advantage is on his side, and Jugo would going to sacrifice his life for him.
Orochimaru could force the rest of the Hokages to fight him.
In this small room Sasuke can easily burn anything and everything in an instant.
Hashirama wasn't really a threat for him and Orochimaru.