Knightsbridge - I think you overstate the quality in the P5 a bit:
ACC (15)- Top end: ND, FlSt, LV, Duke, UNC; Mediocrity: Syracuse, Miami, Pittsburgh, GT, VA, NCSt; Bad: BC, WF, VaT, Clem
Big10 (14) - Top end: MD, IA, Ohio; Mediocrity: Rutgers, Northwestern, Minn, Nabraska, Mich; Bad: Mich St, Ill, WI, Ind, Perdue, PSU (?)
Big12 (10) Top end: Baylor, OK; Mediocrity: TX, OkSt, IASt, TCU, WV; Bad: KSSt, KS, TT
Pac12 (12) Top end: Stan, Cal; Mediocrity: OrSt, AZSt, WA; Bad: UCLA, WaSt, USC, CO, OR, AZ, UT
SEC (14) Top end: TN, SC, TxAM, KY; Medicrity: MsSt, LSU; Bad: Missouri, Ole Miss, UGA, AR, Vandy, FL, Auburn, AL.
I make that 16 top end teams, 21 mediocre teams, and 26 Bad teams. Now people can and will quibble with my definitions and a few teams had a better year this last year than where I placed them and a few had a worse year, but I was trying to think of a sort of two/three year average as opposed to just what this past year showed.
Looking at the rest of the basketball universe obviously Uconn is a top team and I am not sure there is another in the rest of the conferences, but the 'mediocrity' is probably something like this: Albany, USF, Temple, GWU, Dayton, FGCU, DePaul, Villanova, StJohns, Seton Hall (?), Liberty, JMU, WKy, MTSU, SoMS (?), GB, Princeton, Quin, Marist, WichSt, Chattanooga, ETenn(?), SDSU, ArSt-LR, ArSt (?), Gonz, SD (?) That works out to 26 teams and you could add a few or drop a few out.
Interesting to me in looking at the NCAAs - 32 teams are conference champs which leaves 32 teams getting in on merit. The P5 automatically get the rest of their top end teams in so 11 auto-bids go to P5 elite teams. And of the non-P5 conference champs something like 11 each year are 'bad' teams in conferences that would be excluded if the auto-bids didn't exist. So the pool of mediocre teams that get at-large bids is made up of 21 mediocre P5 teams and the 27 top end/mediocre non-P5 teams that didn't get auto-bids or about 16 teams. All this is a long way of getting to the break down of this years 21 mediocre at large bids was:
16 of the mediocre 21 P5 teams got in = 76%
5 of the 16 mediocre non-P5 teams got in = 31%
Some disparity is justified but this lopsided result is more the result of SOS and the 'brain dead' RPI that are both heavily weighted toward P5 teams. I think you see the results in the NCAA tournament most years where a lot of the 'inferior' other conference teams play P5 elite teams more competitively than many of their at large bid mediocre teams consistently did.