Just kind of a point though, you say that Texas' defense is only good for 11th in the SEC, but you need to take in to account that the offenses are much better than the offenses (can you even call them that?) in the SEC.
Vandy=117th scoring offense
Tennessee=115
Miss State=113
Kentucky=105
Auburn=102
South Carolina=97
Sure the SEC defenses are slightly better, but it's clear that these teams would have an awful offense no matter what, so it pads the defenses stats.
You could probably say the same for the Big XII though, but the defenses are at least competent from what I've seen. We'll see come bowl season I guess.