The Pats offense helped last year's defense. It is easy to defend a team that has become one dimensional and forced to pass down the field a lot when the offense has gotten your team a 3-4 TD lead in the first half. They were not nearly as good as the 2004 defense. The red zone defense was suspect last year too like this year. The defense didn't have to win any games last year either.
I am not taking away anything from the 2007 team, but the 2004 team lost only one more game than the 2007 team. Brady doesn't make two stupid passes in Miami and Dillon plays the Steelers' game and that team might have gone 19-0. So let's not take anything away from them either. And they didn't have nearly the offense the 2007 team had to work with. They had to win with both sides of the ball. They were the more complete team no matter what stats suggest.
That 2004 defense wasn't as good as you are making them out to be. They weren't like that 2003 team. They did a great job against Indy that year in the playoffs, but remember that had just as much to do with the weather and the ability of the running game to chew clock. Even if you look at that Miami game in 2004, sure Brady through the pick but it was the defense that let up the winning score.
Again, its not just about the stats. Do a player by player comparison of the defensive starters and I think you have a hard time saying one is that much better then the other either way:
2004 Seymour, Wilfork, Green, Vrable, Willie, Bruschi, Phifer, Gay, Samuels, Harrison and Wilson
vs
2007 Seymour, Wilfork, Warran, Vrable, Thomas, Bruschi, Seau, Hobbs, Samuels, Harrison and Sanders