Bortles actually played well in the last few games of the season. I don't think he'll ever be a playmaker who elevates his team, but he might be good enough to win a SB.
I agree about the defensive line, though. We'll see what Jackson and Campbell do this season.
So it's obviously subjective. If the player loses at the snap and never recovers, or gets physically dominated throughout the play, etc., that's a dominant loss. Turn the tables, if a player physically dominates the play, beats his man decisively, etc., that's a dominant win. You know it when you see it. (One caveat is if it looks like the player missed an assignment or blew a play, I don't give a 2 on that kind of play. For instance, a RB misses a protection, but catches a dumpoff and goes 50 yards while breaking 3 tackles. He still missed his blocking assignment.)
Nelson's whiff on the third(?) play was a dominant loss; his pancake on the pull block was a dominant win.
All JMO, subjective.