It occurred to me watching the last few games (SF, Pitt, Miami) that teams manage to do something a little different that slows down the Bills. The difference between this year and last year is how quickly Daboll & Allen diagnose and find the exploit to whatever it is they are doing. To use a very geeky reference, this year it's like the Borg adapting their shield modulation. You get a few shots in and then they solve it within a series or two, and then what? You just spent a week coming up with a plan to stop this offense (Insert Mike Tyson quote here).
The reason you draft and develop a QB as gifted as Allen is, as another poster noted, he forces the opposing defense to defend every green blade of grass on the field. That's why KC and GB do what they do; they can attack from anywhere to anywhere. Short, long, middle of the field, outside the numbers. The physical gifts of the QB allow a proper scheme to attack any defense successfully in some way.