Howdy...been a while since I've been on the boards but here goes.
I have a fair amount of expeirence as a SE and QB (truth in lending...not a great QB by any stretch) at the HS and college (DIV II) level. I think most of us in this thread have identified that the troubles really aren't just one area or person. I think that's a good sign we can have an intelligent discussion on this by the way.
If you think about the "average snap-to-pass" time folks on the board like to throw around (I think 3sec is the vogue time) that means a lot of things have to go right or at least not wrong, if you catch my drift, to get a simple completion.
Ref. the Oline...you never want pressure in your face as a QB. Many of the hurries and sacks on DC come up the middle either by way of delayed blitz or a stunting/looping DL. You can deal with pressure from the outside much better. I'm not the best to break down the OLine so I'll leave things at that; in fact I think Michael Irving said it best when he said, "OLine is simple, you with fat butt, take your fat butt and go over there and block that other guy with the fat butt".

(yeah...I know it's not that easy!)
While the Oline is working (for 3-5 sec) the receivers have to SEPERATE from the defender or find the seam in zone. One of two things prevents this, 1) your covered by multiple defenders (ie AJ), or 2) you suck (all other options on the team). 7 times out of 10 if you ask DB to cover a WR for more than 4 seconds the offense will end up "winning" that down. The fact is that hardly any of our weapons were seperating from coverage during the game...kudos to TE Bruener for his catch over the middle (maybe the only one all season

). That is how you deal with Cover 2...a big target in the middle of the field. Oh, yeah...Gaffney, take notes...I don't give a d*** what play is called or what route you think your running keep your head on a swivel and if the QB HITS YOU WITH THE BALL YOU CATCH IT! It's is pretty easy to understand how DC can lock in to 1 or maybe two options there by keying the coverage to slide over when you don't have anything else going for you.
As for Carr...I personally think he is trying to do to much. He desperately needs some other playmakers to work with him (other than AJ). He does need better pass protection (including backs and TEs!). My best take is that he is a product of his professional enviroment...you can play the what if game and ask how you think he would have developed with a better coaching staff around him. I actually think that JP Losman is in a great position with the current Buffalo staff and in particular the QB Coach...Sam Wyche. Just my two cents but I wouldn't mind bringing back Wyche to be the O Coordinator. Ok...back to business, no matter what the reason the QB play still needs improvement. There are many things that could be worked on but to me the bottom line is that he doesn't trust (rightly or wrongly) his protection and anyone but AJ or DD with the ball.