That kind of complaint is just crybaby nonsense. WAAAAAHHH, "he wasn't even all-conference his senior year".
Yeah, and whose fault was that? His coaches, or the voters? The two guys that got first-team and second-team Pac 12 that year were Tyler Huntley from Utah and Anthony Gordon from Washington State.
Let's take Anthony Gordon first. Washington State went 6-7 that year. WSU started off by racking up stats and wins against OOC New Mexico State and Northern Colorado and Houston, and then they went 3-7 once the Pac 12 schedule started. Anthony Gordon got "2nd Team All Pac 12" off volume alone, for a bad team. Outside of the 63 points scored in a loss to UCLA, WSU only managed 13, 34, 35, 20, 13, and 21 in their other 6 losses. Anthony Gordon went 493 for 689 attempts, with 5,579 yards, and 48 TDs against 16 INTs. Volume, volume, volume for a losing team.
As for Tyler Huntley, at least you can say he played for a good Utah team. Which, of course, lost to Herbert's Oregon team for the Pac 12 championship. Huntley went 220 for 301 attempts, for 3,092 yards and 19 TDs against 4 INTs.
Compare that to Justin Herbert, who went 286 for 428 attempts, for 3,471 yards and 32 TDs against 6 INTs. In every statistical measure (except maybe INTs), Herbert beat Huntley. The ONLY area where Huntley was clearly superior to Herbert was in rushing, Huntley had 290 yards and 5 TDs to Herbert's 50 yards and 4 TDs.
So I'm not sure what you think Herbert could have done to convince the Pac 12 voters to make him 1st or 2nd team All Pac 12. Was he supposed to throw the ball 261 more times (nearly 20 more times per game) to match Anthony Gordon? Was he supposed to run for more yardage to match Tyler Huntley (since he beat Huntley in passing stats AND the actual head-to-head game)?
I'm just not seeing "not all conference in his senior year" as being anything that Cristobal/Arroyo could have changed. Outside of the first game neutral-site loss to Auburn, Oregon lost ONE Pac 12 road game, by 3 points. Oregon won the conference and the Rose Bowl. **** good season.