It was mentioned many times before that immunity just doesn't work in this SA. Also- when it comes to lvl hard of it- Sasuke has unlimited initiative so it's impossible to interrupt- but you still can do it with, for example, Guy on normal lvl.
Yes it is very hard but people already came with many ideas of line-ups to beat it. I personaly switched to Lighting main and beat it pretty nice on hard with team of Kurenai, Iruka and Guy. Just one of ideas, there are better ones too.
Tho, they could add information about some stuff that are part of it somewhere- like that immunity which doesn't work, 'cause at first, when player don't know this SA yet- it looks like bug :S