First, if the regular season is irrelevant, can you tell me which teams will represent the Pac-12 in the NCAA Tournament? If not, then it sounds like the regular season is very relevant....at least for 7-8 teams in the conference. Even if you know your team is going to make the tournament, history tells us that seeding is important, where you play the games are important, how the last 10 games of the season are figured into that seeding. All of that makes every game important.
In college football, if a championship is the ultimate goal, then you can honestly say that the regular seaon is irrelevant for about two-thirds of the teams that will never have a shot at a national title, even if they go undefeated. That sounds irrelevant to me.
There are too many teams in the NCAA Tournament, but that is still better than wondering each year if you have a legitimate bowl championship game.