[Sasukemaru]

I'm not saying she can't burn through susanoo, I was just saying sasuke was severely weakened when they fought. However, there are plenty of one hit kills like hers, so even though her jutsu is powerful, a "I can't get hit by that" type of technique is not uncommon in naruto. Even though I believe mei could burn through susanoo, madara made no effort to try and stop her or any of the kages attacks. I got the sense he was gauging their powers, more then mei caught him off guard. Besides, every high level ninja who has gone up against susanoo has gotten past it, danzo, mei, gaara, tsuchikage, raikage. It's not so much an impenetrable defense as it is a counter attack. I mean, the opponent is incased inside a huge ethereal juggernaut that defends him, and can crush your whole body with one blow.