1) Sports Strategy 101....change a losing game.  Who knows if Herbert is "able to carry the Ducks" but we will not know until we try. Plus one issue is for certain: Prukop is gone after this season and presumably, Herbert will be here next season. 

2) No it is not entirely Prukop's fault but in the bigger picture it is the fault of the coaching staff for this consecutive season "strategy" of thinking FCS level quarterbacks can come in and consistently play at FBS levels. The coaching staff either A) Failed to recruit an FBS level QB so that is on them or B) Were unable to coach the players they did recruit to an acceptable playing level...again on them. 

This is more of a coaching issue than player issue.