As it stands now, was the Big Ten overrated heading into the tourney? There's several ways you can look at it. If you look at the seedings of all the teams, you can determine how far each team "should" have gone assuming the higher seed wins every game leading up to the final four. 0 means teams won as many as expected, a + means they won more than expected, and - means they won less than expected:
Indiana -2
Ohio St. 0
Michigan St. 0
Michigan +2
Wisconsin -1
Illinois 0
Minnesota +1
Add it up and it equals 0. That would mean at this point the Big Ten has won as many games they were "expected" to based on seedings. Just for comparison, the Big East is at -2 not counting the Louisville-Duke game.
Another way to look at it is to base it on your opponent. If you beat a team you were expected to or lose to a team you are expected to, that equals 0. For every expected win or unexpected loss, you get a + or -. The only thing that would change is Ohio St. would go to a -1 because, even though they made it to the E8, they lost to a lower seed. So it essentially means so far the Big Ten has been upset one more time than they have upset an opponent.
Some could say it has been a mildly disappointing tourney for the conference, but overall it has been pretty solid.