The line was regarded as one of the best in the nation for two reasons:
1) Allowing 4 sacks last year, and
2) Having pretty much everyone carrying over from last year
The major problems are this. The "best in the nation" tag came because of statistical idiocy; people looked at the number and said "Wow, four sacks! They must be great!" and went with that. It overlooked all the components of the offense that went into creating that obscenely low number. The second part is the unspoken assumption that experience from the prior year automatically carries over and will improve even further.
As I pointed out in another thread, the offensive line play from about 2003 to the present has been horrifying. To quote those posts:
The real problems the last few years have been on the offensive line. I can't believe the technique that's being used; if it's being taught that way, then fire the coach, and if it's not being taught that way, then either get new players in there or else devote more practice time to it.
Most linemen coming out of high school have been able to strictly rely on their brute strength to be able to block, which doesn't fly at the college level. And yet it seems like the last five years has just been "forget technique, let's focus 100% on the schemes", to the detriment of the offense as a whole.
There's a lot of what I refer to as "the grab and steer". What it involves is the OL grabbing the DL under the armpits and more or less steering him one way or another, leg drive optional (and rarely taken).
What it totally overlooks is the fact that, in the running game, a stalemate goes to the defense. The purpose of run blocking is to open up holes for one or more backs to get through and provide them the most room possible. A good DL coach will teach his guys that there's nothing wrong with a stalemate; in fact, it should happen in roughly 80% of the line battles over the span of a game. That's an enormous benefit to the defense; it allows LBs to fly around in the run game and make plays all over the place.
The grab and steer results in a ton of stalemates, because with that "technique" it's literally the best that can result. If the best that can happen is something that favors the defense, how on earth can it continue to be taught and accepted?
Good line play has three components:
1) Violent punch -- it should rock a DL back on contact
2) Work to extension -- same logic as an RB stiff-arming a defender; it uses all the large muscles of the arms and provides separation
3) Leg drive -- Because, after all, you're trying to move someone from a place he doesn't want to vacate
Until there is a coach at UT that teaches and continually hammers on these points, the offense will struggle no matter who's calling the plays.