Based on kenpom numbers, Duke is an incredibly weak #2 seed. In the kenpom era (2003-), these are the three #2 seeds whose kenpom numbers were in the same ballpark as the 2012 Duke Blue Devils: 2003 Wake Forest, 2006 Tennessee and 2010 Villanova. Let's look at how they did in the tournament (or just look away now if you are a Duke fan and have a weak stomach) -
2003 Wake: Beat #15 East Tenn. St. by 3 and lost to #10 Auburn by 6
2006 Tennessee: Beat #15 Winthrop by 2 and lost to #7 Wichita St by 7
2010 Villanova: Beat #15 Robert Morris by 3 and lost to #10 St Mary's by 7
I swear I did not pick these three teams knowing that they performed similarly in the tournament. I just looked back to find teams that were similar in ranking to Duke and also placed on the #2 line and then found their results which are strikingly consistent (and deeply troubling if you are a Duke fan).
Only 2003 Wake (0.8928) and 2006 Tennessee (0.8897) are behind Duke (0.8971) in kenpom ranking but their numbers include their putrid performance in the NCAA tournament [2010 Nova ended up at 0.9011]. I would guess that at the time of seeding, Duke is the lowest rated #2 seed of the kenpom era.