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

It doesn't matter to the devs but this SA is garbage. I've already been VERY disgusted with the game with the recent merge of servers on events mainly due to the imbalance but this SA? I'd like to tell the devs where to put it but that wouldn't be nice now, would it.:@