I was wondering the same....what I've been noticing is that the further you get from default, the less frequently the offline throws happen. On the OP, I easily get 5-6 misfires per game (per QB) and probably another half dozen (per QB) that are not quite misfires, but off the mark.
If incompletions are coming mainly as a result of drops and batted passes (and I am not saying they are due to small sample size); that would definitely kill it for me...