I don't think we should be making a "who's going to be the D/C" decision based on who makes the most as a position coach. Both T-Rob and Durkin may make outstanding defensive coordinators. But we don't know that for sure, neither of them has had that job yet at a major college program.
Hadn't been thinking about Randy Shannon, but that's a very interesting idea. He's run really good defenses at Miami, sent a lot of players to the pros, and probably is the creme of the crop in terms of knowing the recruiting landscape in south Florida. Pretty much got rid of Thug-U culture when he was at Miami, which had to have been very difficult. As far as I know, he pretty much did everything the right way down there, except not win enough games. He's way too good to stay as a LB coach at Arkansas very long, somebody's going to snatch him up, and it might as well be us. I'd rather have the proven Shannon as D/C than either of the unproven internal (apparent) candidates, T-Rob or Durkin. Let them get their D/C seasoning somewhere else first.
Not that I'm making any decisions on coaching staff, of course.