If you took away one-and-dones (players the MWC has no chance of getting), those NBA numbers wouldn't look so bad for the MWC. If one-and-dones stayed 3 years, the regular season numbers would benefit the Pac-12 more.
I would say the Pac-10 and WAC were pretty evenly matched in the first 10-15 years post-Wooden, and you can make arguments that the WAC was superior. Where the Pac-12 really gained separation was the emergence of Arizona as a national power, in the mid-late 1980s. In fact, it wasn't until 1982 before a non-UCLA team made a regional final (Oregon State, 1982). Counting Wooden's last year, three WAC teams made it to the Elite 8 (ASU, Arizona, BYU). 1983 Utah was probably the weakest WAC rep in this era, yet it beat UCLA en route to the Sweet 16, and the Pac-12 that year was only a two-bid league.
UCLA notwithstanding, the idea of the Pac-12 as a powerhouse basketball conference is a relatively recent phenomenon, and it has never had the year-in, year-out strength of the ACC, Big 10 or old Big East.