re: Is Bama D susceptible to an up tempo offense?

In comparison to other defensive strategies, I would say that the Bama D is actually designed specifically to combat up tempo offenses. The defense was built with the spread and no huddle in mind really. You'll never see the Bama D huddle up because you can't do it when playing an uptempo team so the coaching staff doesn't want to make it a habit. Also, there are different color-coordinated personnel groupings for different situations, even if it's the same or a similar play call, so after a play all the coaches have to do is call a color and the right guys come off the field and the right ones come on the field (offenses are required to give the defense adequate time to substitute as we saw last year in the Oregon-AU game).

The structure itself is designed to be effective against this strategy, after that it all depends on the players.