I guess the objective is to not rely on any rookie QB to be your guy since (apart from top 5) they are all unlikely to succeed.....perhaps drafting a non-1st rounder every 2 years until you see something you like....ala Brady, Bulger, Romo, Hasslebeck etc, etc, etc. is the way to go.
It seems to me also that the success of teams forced to use their late round draft picks as rookies due to injury to the starters do not seem any worse affected than most teams going with rookie 1st round picks.....i.e....Orton(Bears) last year, Gradkowski(Bucs) this year....both not doing good but relatively similar to Leinart this year or Smith(49ers) last year.