I'd be sympathetic to the argument that USC doesn't play in a tough conference, but computer systems that look at who played who - basically a comprehensive look at common opponents - much as you are doing by comparing schedules to the Big 12, SEC - say that only Oklahoma was better during the regular season, and then we saw who was better "on the field" - as it should be. And, my, was USC better!
May I weasel out of that one by pointing out that Auburn was my pick for USC opponent? Nah? Didn't think you would let me.
To be fair, I don't know if Auburn would have beaten USC. They were superb that night
My point is, still, that the Pac 10 is a weak conference, and a mediocre team looks like a winner, like a scrub oak looks compared to tumbleweeds.