I would say this .... if you believe in a quarterback, really believe in a quarterback, you should be willing to use a Top 5 pick on him no matter what. And if you don't really believe in a quarterback you probably should not draft him.
In 1992, Brett Favre was generally rated as an early second round pick. That's where he went. But Ron Wolf and the Jets had Favre as the No. 1 overall player on their board. Had the Jets had the No. 1 pick that year (or any first-round pick), they would have used it on Brett Favre, even if he was a second-rounder to everyone else. And they would have been right.
Wolf, with the Packers, traded a first-round pick on him next year, for a guy who had thrown five passes and worn out his welcome in Atlanta. The rest is history.
I don't know if the Cowboys rate Lynch that highly. I don't. But if they do, I have no problem with them drafting him at 4.