Thanks for posting. A few thoughts (not being nitpicky, just my own opinions):

I think Tom Brady skews things.
I also agree that more JAG QBs made it that far pre 2010 because of league rules and the emphasis on the passing game.
Back in the 80's a strong defense and running game would get you far. I'd expect more RBs drafted high back then.

Many of those QBs aren't JAGs... they may not have been elite but they were top 10-12. Donovan McNabb, Steve McNair for example. Earl Morrall won MVP in 68.
I think the number on Gary Kubiak is iffy, if he played that many it was as a kneel-down/mop-up QB. Might be the case with a few others.