He has potential. Skating and stick handling is elite. However at this point, I don't think his lack of defense makes up for his offense. He's high middle in points on team and has worst - And he isn't out there on kills or against top lines. He isn't even on 1st PP. If he doesn't shore up that part of his game, I see low first round at this point.
+/- is a mostly worthless stat.
He doesn't PK because he's the other 4 RHD are all bigger than him and its a very solid defensive group from a defending standpoint. I really don't see Casey as a bad defensive player. Can he be overpowered? Sure, but I don't see big errors with regularity. I actually think he's a quality defender because of how hard he is to forecheck. A bigger, stronger, faster player will throw it in behind him, and he'll make a good decision to relieve pressure.
And I've started to not make much of the PP units they use at the NTDP. Look how poorly they are mismanaging them with the U18's. I think the units are more for development purposes than anything with winning being secondary. And who on that defense is a better PPQB than Casey? I'm not sure there is one. PP units if I was running it would be Casey, Chesley, McGroarty, Nazar, Gauthier as unit 1, Hutson, Kaplan, Fleming, Howard, Cooley/Stramel as unit 2.