Let me first clarify, I am looking at Dennard purely from a Patriots defensive scheme perspective. Another team may find his aggressiveness appealing but I just have not seen the Patriots run their scheme that way. It seems the Patriots would much rather keep the ball infront of them rather than go for the big play.
Back to Dennard himself. Living in the midwest, I get to see my fair share of Big10, Big12 football and I here is what I have taken away from Dennard.
Outside the physical attributes is where I think he excels. He seems to have good instincts, is a good tackler, seems to have good speed.
On the other side I don't really see him as a playmaker for the risks that he does like to take. He only has 4 pics in 4 years. He is awkward in his back pedal and is really bad in his transition. He struggles to make the turn and run which takes away from his timed speed that he will show off probably at the combine. Does better in press coverage I agree, but I think the Patriots don't really prefer to play press coverage, and that is why having Dennard in the first for the Patriots just seems wrong.