omnifinite

If the person with the knife is trained I bet anyone would be in trouble. Your average moron would probably be waving it around, but someone who really means business might be smart enough not to even let you see they had a knife until it was too late. Plus people who are trained will probably slice any part of you that gets near them, rather than specifically going for vital areas. Getting cut as nastily as they'd cut you is traumatic enough to weaken you psychologically... then they're free to do the real damage. I'd rather never find out. We've been ruined enough by action movies to think that's ever a harmless situation.

From what I know kata were originally ways of practicing your techniques in secret without giving them away to people who may be watching. In your mind you know what every move may represent... but an onlooker can't decipher what you're doing. Think of each kata as a catalog of techniques. It's as much a mental exercise as physical... and if you've only been taught the physical kata and not what's behind it, then, yes, it can be a waste of time. I think in a lot of schools this has been forgotten.