i'm not a big duke guy but, they do own the 2 best wins anybody has had all season...
They beat both teams that played in the Big 10 Championship game. They have also beaten a lot of teams in the Top 25 and/or are in the field. Beat Virginia, UNC twice, Louisville.
I'm not a Duke lover or apologist, and you can certainly make the case as to why they are a #1. Wisconsin would have been a #1 even with a loss on Sunday, so conf championship tourneys are not the end all, except for the smaller conferences.
I would have given that spot to Arizona if you're looking to replace them.