Alabama is really good at football. That might not sound like useful insight or deep analysis, but it is. Alabama isn't just good on defense. They aren't just good at running the ball, forcing turnovers or kicking field goals. Alabama is very good in almost every aspect of the game, and they are elite in many.
For example: I bet you could guess that Alabama allowed few explosive plays, especially against the run, but did you know Alabama was one of only five teams that gained 25+ yards on more than 10% of pass plays? It might not surprise that only Army was stuffed less often when running the ball, but T.J. Yeldon was twice as likely to gain 10+ yards as he was to get stuffed. AJ McCarron threw interceptions on fewer than 1% of passes and Alabama was 7th in interceptions per pass attempt against. Finally, Alabama was tops nationally in points/possession allowed (.86), but you might not have realized that Alabama was 4th in TDs per possession on offense.
Alabama was the best team in the country in 2012, and for most of the season they were in a league of their own (Texas A&M made a strong run at them at the end of the season). But even so, they needed a significant amount of luck to win a national championship, and they needed even more in 2011. Texas A&M gets their shot at the champs early, LSU late, and then 'Bama will have to hold of the East champ. If they lose any of those three, they'll need a ton of luck to get back into title contention. If we give them an 80% of winning each of those three, they'd have only a 50% chance of staying undefeated. In other words, as good as Alabama should be, I'll still take the field.
One more side note. The EPA+ has an incredible track record of picking Heisman quarterbacks (and identifying the top running back contenders). McCarron finished with 125. That's good enough for 17th overall, 100 points behind Tajh Boyd and about 40% of Manziel. I'm not saying McCarron can't win the Heisman, but it would be a significant deviation from recent Heisman voting trends.