Alex Kostic 2007 Melboune Seminar - Multiple Attackers 

You don't need vision all the time. With shoulder blocking You can without effort make good shot at the same time, so the attacker won't even realize he did not landed his shot ;). Besides, if You can feel Your opponent through physical contact, You don't have to see him. Systema is more body movements than exact technique. And that's very exciting to learn, especially when teached by good trainer as i've got :).

I havn't actually seen alot of systema. I personally think that the shoulder roll blocking system isn't that great because it takes your vision off your target even if it is only for a second. Good video anyway, cheers

I like the idea but I find that with me I tend to get overwhelmed when my field of view is obstructed while sparring

I've been training for a long time, I think it's unnecessary to train a move that puts you in a vulnerable position. That's just me though, we all have different things that work for us