You need to throw out the Texas game because we had key players not playing that game on defense and the offense was terrible that night. I am not sure that we had our heads in that game because of the implosion against the Ducks.
The USC game is interesting. They decided to throw deep all night long and Blackmon was not healthy in that game. I think that an injured Blackmon played a key part in the USC and Oregon losses.
You are right that the 2008 team played a tough schedule in TCU and Alabama and both of those games the D stepped up. I am not saying that the 2008 D was not great, but IMO the 2019 still remains the best. But, I realize that it is all subjective.