I very much disagree with your definition of mediocrity. Mediocrity is just meh, it's neither good nor bad, it's the very definition of ordinary, average, pedestrian, etc. It's not necessarily failure but it does include the absence of significant success.
Consider: distributed to members of the (arguably) top 5 basketball conferences (Big East, Big XII, Big Ten, SEC, ACC) there were something like 30 bids to this year's NCAA Tournament drawn from around 60 total schools. Thus the probability of any given program from one of these conferences reaching the NCAA Tournament should be roughly 0.5 since that's probably been true for the top 5-ish conferences essentially forever.
So a mediocre coach from a top 5 conference should, based on probability alone, make the NCAA Tournament about half the time. The perennial bubble team is therefore mediocre by definition. If the team falls so far off the bubble that they don't make any postseason tournament that's not mediocrity, that's failure.
Consider Weber's last six seasons at Illinois playing with his own recruits: 3 NCAAs (50%, the very definition of mediocrity), 1 NIT & 2 seasons with no postseason play. That's mediocrity in a top 5 conference. It's neither bad nor good, it's just a little less than average.
Wooly & Asbury weren't mediocrities, they were failures. Particularly pathetic ones at that.