You're insane. Had Marlon come out last year he would've been a 1st -3rd round pick by every account. He did everything right at FSU and was a leader on that team. The guy has all the physical skills in the world. 3rd team All-American in '08, 2nd team All-ACC. Average players do not post games like the following: 4 tackles (2 touchdown saving tackles), 1 tackle for loss, 4 pass breakups, 1 sack, 2 quarterback hurries and 3 critical 3rd down stops. And that was in a rivalry game against a good Miami team.
On researching it a little more, the question was whether he was committed to the game enough after taking the year off. I don't get the concern though. I don't know many that would pass up the opportunity to study at Oxford free for a year.
Again, the concern is where his devotion lies. Judging by how well he balanced football with academics at FSU, I don't think there will be any motivation issues. The draft is finicky like that though.