I think i'm right in saying that people who crash and burn in normals will just run LFR instead or quit the game, it's generally only the very keen or people with a definitive issue who ever post on any of the various forums.
Your post is also a bit of a loop - you say that guilds should recruit with harsher criteria so they can pass the test that is normal modes, and then say people are failing because they didn't set the test. it's not like a test or application in and of itself grants the skills needed to pass it, all it does is dismiss from raiding anyone who can't make the grade.
A universally used application test would indeed put the percentage of successful raids up but at the same time would crater the total amount of raiders. Again, I see this a lot - hardcores remove anyone they find unsuitable to associate with and then completely forget the person they excluded still exists. Johnny Clownshoes who doesn't make the grade for normal modes probably carries on playing - doing LFR and Bg's and dailies - he's just waiting for the raids to come down to his level so he can do organised content once more.