I think this is the key point for discussion, really. If you can't make the system (not necessarily individual techniques) work in some kind of relatively open sparring, it probably has issues - or you do. That's no guarantee it's going to be useful in any given defensive situation, but the odds are better if it works in sparring. And there's really only one way to know that answer.But....bottom-line....fighting is fighting. If someone has problems getting their martial art and what they have trained to work in a sparring situation, they are very likely to have trouble getting it to work in a real situation.