TCU went into yesterday's game with a top-10 D, and that was after playing OU's offense. They've finished in the top-5 in total D several times in the past 8 years, including twice at #1. Gary Patterson is widely considered one of the premiere defensive minds in the country.
I don't think I've ever associated "bad defensive teams" with TCU. Not a great effort, but I definitely think it was more a spectacular offensive performance then "bad defense".