To be fair I think he has a bit of trouble at the top of his rush due to a lack of strength to absorb the contact from the OT and still power all the way through to the QB. He was around the QB a lot, but there were also plenty of "close but not quite there" rushes, even if he had beaten the OT to their edge and even if they did affect the QB.
He also got a few of his sacks as a looper on stunts/twists, which he is actually quite excellent at, but it's not a pure, beating the OT around the corner edge rush.
He's relatively raw as far as his pass rush plan as well, mostly relying on his speed/burst to beat OT's around the corner, although he does flash an effective spin, rip and swipe on occasion. I look at that as a positive though, if he's affecting the QB with a relatively raw repertoire of pass rush counters then there's plenty of room to grow, and given that he got the 18 at LSU his work ethic is definitely top notch to maximize his potential.
All in all, I'm not saying we have to take him at 17 under any circumstances, I'd still prefer trading up for Kinlaw/Brown or down depending on the board, but if it's Chaisson vs. Henderson at 17, give me Chaisson all day, with McKinney after that.