Well, defensive coordinators in general catch up to what offenses are doing in the second half of the season, so it's up to offensive coordinators to keep defenses guessing.
My guess is that DCs began to understand what Drew's weakness were, and what our offense's weakness were, and how to exploit them, and we (Drew, offensive coordinator, and offense in general) didn't have the talent/ability/whatever to make adjustments.
I think his situation in Dallas is different, because I think Dallas has some decent talent at RB, WR, and on the O-line, as well as Bill Parcells calling the shots. Their weaknesses are not the same as ours were then, plus they have a smart coach who understands their weaknesses and can adjust.
We'll see. But then again, it's Dallas, I hate Dallas, and I couldn't give a rat's a$$ about Dallas.