I think it's arguable that CJH whiffed on Joe Milton III, not that Joe is bad but not a great fit for Heupel's offense, and Nico, perhaps similar to Joe..... remains to be seen.
If Merk and McIntyre "have trouble seeing the field as well as Hooker did" also, you have to start to scratch your head and wonder if CJH is picking the right QBs for his offense.
The offense is supposedly simple reads and execution, granted at a fast pace..... but Heupel has slowed it down a lot in the last 2 years. I'm having a hard time thinking Joe wasn't ready, Nico is not quite there yet, Gaston Moore lacks the talent to execute a simple offense....... and I'll be really questioning if Merk "can't get it but he's really young" and then McIntyre "hasn't really played enough to have it down yet."
Heupel isn't in danger of losing his job but he may be in danger of peaking in what he can accomplish.