"It's not a lot of bias, it's just the numbers."
RPI = garbage in, garbage out. Someone has to give a base start value to each team, and the system is rigged.
There are fewer Western teams. The Big West, WCC, MWC and Pac-12s all play full round-robins, so they can't skip a powerful conference opponent. They also pretty much play each other exclusively in OOC, so they will incur more losses , since there are fewer conferences to play. Most Pac-12 schools also play two OOC games against their traditional rival, instead of a regional cupcake, so that's 10 more losses over the course of the season. They also don't get to beat up on a bunch of A10, MAAC, Ivy, NE Conference, MAC or other schools from the Northeast/Midwest who can't practice outside before they head south to open their seasons, in February and early March.
NC State was 35-20, played ONE OOC game against a Big 5 opponent, played 30 home games, had only 12 road/neutral wins, and has an RBI of 10.
Oregon State (to use an example), was 35-19, played EIGHT OOC games against Big 5 opponents, all on the road or at neutral sites, had 18 road/neutral wins, and has an RPI of 44.
The SEC and ACC are excellent baseball conferences. But the lower 2/3 are always way overvalued in terms of RPI.
Are the Pac-12 and Big West as strong as they have ever been? Probably not this year. But they certainly merit one regional, and probably two, and have more than proven their strength in the NCAA tournament over the past 50 years. .