I think it is you who is clueless regarding Pryor's QB ability. He has as good a chance of being a good NFL QB as any of the QBs in this year's draft. Cam Newton, Jake Locker, Christian Ponder, etc. -- which one is clearly better. None.
I don't know if he will be an NFL QB, but how many of the QBs drafted turn into good NFL QBs? Not many. I think Pryor is worth a shot. Why would it hurt to draft him in the 4th or later? I would not have drafted Newton or the rest before the 4th.
But then again, I am apparently not as great a talent evaluator as you. Which team do you work for?