There are a lot of little technical things wrong with his logic. And yes, drafting players is a crap-shoot, although we can sometimes accurately guess which players we or will not be drafted based on team scheme.
For example:
Although Otah may be a physical freak, he's still probably not the type of lineman the Broncos would draft. They don't really have mauler body-types like Otah, but smaller lineman. In fact Otah out weighs the Bronco's lightest lineman by around 50 lbs. So I think that's a bad call.
McManaman also calls the Raiders defense "stout". He's half right, they can be stout, but they need more talented personnel in the interior of the defensive line than they have. Otherwise they'll be just as underwhelming as they were last year.
The Chargers won't take a RB in the first round to complement Tomlinson. As cool as Sproles is, he's probably not the backup answer in the event of injury, so yes the Chargers may draft a RB, but in the first?!
Like Skkorp said, the author has a chance at being right. If he wins it'll be more luck than skill.