I think he's better than he's played, but that's an opinion and not a fact. I trust PFF's judgement.
The point I'm making is that teams can expect whatever they like, but there are like 3 number 1 receivers without question marks. I wouldn't be upset with Cooper had the Bills drafted him at 15.
Cooper is immensely talented, and just 24 years old. It wasn't an awful move by the Cowboys. This is not a Doug Jolley situation.