Obviously, it's very debatable, but in his 16 years, I don't think he's beaten (other than St.Mary's, but are we really going to pound our chest about beating a 7 seed St. Mary'?) a seed more than 1 see higher? But, he's been beaten by lower seeds more often than he's beaten higher seeds.
The main reason is, he hasn't had elite guards (until Carsen comes along and look what happens). Guard play is the most critical position in the tourney and Painter just hasn't been able to recruit enough difference-makers at the position.