It's more a problem of the player mentality. Pugs have some disadvantages most people in pugs doesn't mind. You play with people first time you never played with, everyone has a different experience over the content. Also pugs are very fragile. You are not bound to everyone, there is no guild mentality in there so, some people don't care about what the raid leader says. Especially for x-realm groups these problems weight even more.Or are most players in pugs just not good enough?
And yes, some people are ridiculous stupid, but that's a side problem.