It would be interesting to see the data at different yardage intervals. It seems that being behind the sticks as much as Allen was, would require him to make longer throws more often. Longer throws with a bad o line equals a lower completion percentage. Rosen probably has the same issue.
When you look at Trubisky, Mariota, Prescott and some others, Allen does not look all that different. Yet, you don't hear the sports media harping on their accuracy the way they do Allen. As some of you already observed, some NFL caliber linemen and receivers can make a big difference.
For those of you who haven't had to endure the likes of Todd Collins, Trent Edwards, JP, and Johnson; Allen is a breath of fresh air.