My issue with Hall is that he's a face-up rusher. He wins with strength, length, and effort. (In the NFL, he'll need to add skill to the mix.) He does not bend well. He's not the sort of guy who explodes off the ball, dips under a blocker, and turns the corner. He goes through the man in front of him.
That works extremely well at the NFL level for some guys. But it's harder to project that skillset than it is a guy who wins with speed and bend. Because NFL OTs are bigger, stronger, and smarter than college OTs. The good part of Hall is that he is physical, tough, and sets a hard edge. He'll be a good run defender if he keeps the motor revved. The question for me is whether he's the sort of dude who ends up being a 5-8 sack per year clean-up guy (ex. Sam Hubbard) or whether he can a guy who puts up double-digit sacks fairly routinely (ex. Za'Darius Smith). (Or he could be something in between, like Preston Smith.)