USC is always super-talented; Oregon has speed on wheels; Stanford and UCLA are very good. Arizona State, Arizona, Oregon State, and Washington are all decent (and in any given year, any two of those four are likely to be very good).
I can only think of a few teams that are consistently "dead weight" - Cal, Washington State, Colorado, and perhaps Utah.

BYU is better than Washington State and Colorado (the Buffs are garbage). BYU won a shootout (by one TD) vs a 5-7 Cal team last year, so they're better than Cal, too - but not overwhelmingly better. BYU hasn't won against Utah since 2009; based on almost any comparison (NFL talent, recruiting classes, head-to-head, etc.) we can't say that BYU is the better team.

And which of those other, non-dead weight teams would BYU have beaten last year? USC? Oregon? Do you think they would have won against Oregon State or Washington? The way I see it, BYU would have finished 8th (possibly 7th) out of 12 last year in football.

And what about basketball? BYU wouldn't have beaten Arizona, or Oregon, didn't beat Utah, and squeaked by against Stanford (a team that tied for 5th place and went 9-9 in conference play). I feel like UCLA could have beaten BYU, too. BYU might be 5th or 6th in basketball in that conference - but that's not good enough for an NCAA bid.

And anyway, would you really want to be part of a conference where you're always in the middle of the pack? BYU in the PAC12 sounds like a lot of 7 win football seasons and 18 win basketball seasons, if you ask me...