I should caveat this each time I say but I agree completely and you won't find a person with more respect for Bill Bedenbaugh as an OL coach and developer. I hate that fucker. His lines are consistently among the best in the nation and he can do it with a random assortment of guys with varied skillsets. I truly hoped that Littrell would unfuck his shit and get a big gig and steal Bill B, but no such luck. I also think in the past that OU had some of the best blocking WR in the nation. I think Riley's offense and the guys he's targeted as recruits seem to have changed that dynamic at WR it's just a different scheme and a different type of player and so you get a lot more explosive plays from the WRs and give up a bit of solid ground gaining second level blocking in the run and screen game. I think Riley could supplement some of that loss at WR blocking by taking some bigger RBs that are kind of brutes, not unlike what we've seen from Baylor under Briles. I don't know if he'd give up the playmaking type for the extra power though, it appears not, and his offense is his baby and it's incredibly effective.
You are right though, it's all about the defense and it's inability to compete with comparable talent. I think it's partially player issues (as did Grinch), I think it's partially scheme based (SpeedD's downside). Further, I also have a lot of respect for the results that Schmidt had as a S&C coach and absolutely ZERO respect for the job that Bennie Wylie does. I think those factors along with the sheer number of reps and focus that the O receives in Riley's system severely limit the ability of the defense to have a true physical identity. It's best case, by design, is to disrupt and get off the field a few times for quick change offensive opportunities. That's the focus and I get it, esp combined with that potent quick strike offense. It just leads to being less physical - which leads to being the worst RZ defense in the country.
I don't think it was ever an OL issue but yeah...