Tobirama can make massive water jutsu out of thin air and has massive chakra reserves amplified by Edo- tensei (thus making them unlimited). If he wanted to he could turn that room into an ocean and drown them all - sasuke has good reason to be scared...
Bro what's going on? Usually you're so intellectual, but lately you haven't been using that gifted brain. Sasuke has knowledge on Edo Tensei, you forget he saw Itachi as one! He knows the regenerative abilities and the hand seals! I don't see Edo Tobimara to be such a huge threat. Sasuke is not there for a fight, but only to seek answers.