It would definitely help if the offense could get a boost from the D. Like creating turnovers for short fields. BYU was beat by meh offenses last year because they got easier scoring opportunities. Can't have a fumble or an INT that sets up a meh offense with 20 yds to the EZ, which we did against Utah and USU. If our D forces punts, it can't constantly be after they've had enough of a drive to pin us close to our own EZ. Little things like that will matter. D leads to O. I guess I'm saying our offense can appear better on paper if they get better opportunities to score instead of constant 80 yd drives to score.
That doesn't answer your question, but the D definitely needs to help. And the O needs to help in return by not having the quickest 3-outs on the planet. But it will always be a combined effort. We can ask how good the offense needs to be, but that also depends on what our D will allow? Can we get away with x points because our D held opponents so low? Or are we a Cal/AZ type team where we need to score a ton because our D can't do jack? Hopefully we're balanced. We shouldn't expect one extreme or the other.