I didn't think he did very much in that game. The RT dominated him, even though he did get a sack on him that was a coverage sack. The freshman LT at times blew him off the ball many times in the run game and held his own against the pass. Couple of times he got blocked by the backs or a receiver(#13). I have no interest in Gregory.
He absolutely ate the LT alive a plethora of times, particularly on inside moves. He also stood him up several times when it looked like the LT's responsibility was to seal the outside. He wasn't as good against the run, but that's not why we'd be drafting him.
Very first play in the video he shows a great outside burst and then a good rip move and almost gets the sack.
Second play he knocks the LT back on his heels, takes hands to the face and is right in the QB's face in under three seconds. No one covered the RB though.
@:49 He plays the middle run option, then gets back outside and beats the LT block for the tackle.
That's all in the first five minutes, but it continues...
@1:18 he absolutely whips the LT with an inside move. In the QB's face in two seconds.
By the second quarter they're doubling him regularly.
@3:00 He absolutely beasts the LT to the inside again. In the QB's face in a flash. Forces another early, errant throw.
@3:13 like a broken record, inside move, right in the QB's lap. Forces the quick errant throw.
@3:50 he puts on swim move on the LT that's so good, the tackle falls down.
In the second half, the LT does a much better job, but they also continue to double Gregory a significant number of snaps. Judging by the stats, USC ran the ball more in the second half as well. Gregory also played a lot more against the RT who, like you pointed out, actually did a far better job than the LT did.
I question his ability to hold up against the run on three downs, but Gregory can get to the QB. There really is no arguing that. I hope this tape isn't your best agrument against his ability to impact the passing game. They double teamed him, chipped him with a running back or he was in the backfield quickly on a very high frequency of snaps. The LT did get the better of him 1-on-1 on several occasions, but its asking a little too much for Gregory to beat the guy every play. Particularly against a team known for developing offensive line talent.
Gregory is as close to Bruce Irvin as there is anywhere. The way he plays. His body type. His move set. I'd take Irvin at 27, but thats just me. I can get not wanting Gregory, but the kid can rush the passer. Period.