Lets be honest he wasn't worried at all that battle he could've won any second he wantedMei enclosed an area and Sasuke was weakened and couldn't move that's the only reason that happened. In an open area it would have no effect considering Sasuke's shunshin speed. Vs Madara Mei and all the kage's was getting rek'd and he wasn't even serious about fighting them. But yea she's strong as hell with Byakugou activated but she's still slow as heck. And Madara even while not serious had to worry about the other 4 kage's not just Tsunade also.