Yup, last season is last season. The committee's job is to pick the four best teams. And a one-loss non-champ Bama showed they were better than one-loss ACC and SEC champs.
But the eye test is a huge factor. If Bama loses a squeaker to UGA in Atlanta, it'd likely be down to a one-loss Michigan and a one-loss Bama. Neither team would likely have a marquee win (LSU and OSU are good but not great IMHO). If the committee was tasked with picking the four best teams, it would probably be Clemson, Notre Dame, Georgia (assuming they win out of course) and Bama (in that order). Why? Because I think on a neutral field, Bama would probably beat Michigan (it'd probably be closer than a lot of people think, but the Tide would certainly be favored).
Now, for argument's sake, let's say that UGA completely runs Bama off the field in the SEC Championship Game to the tune of 52-17 (Cincy would love that, even though there's like a 0.5% chance of that happening). If Michigan wins out, the committee would almost certainly put UM in over Bama. As Ohio State proved last year, it's one thing to lose respectably (like they did to OU), but it's a whole different animal to lose ugly. The later in the season it is, the worse it gets as it's fresher on the committee's mind.