There aren't 10 dominant defenses in this league...
Every year is different...there is no formula...you just need to be good enough to win every game in the postseason...it can be done In many different ways
Absolutely.
One of the problems is that people see defense in a vacuum, totally apart from the rest of the team, which is not the case.
An offense with a dominant run game and high percentage passing limits the number of snaps a defense has to defend.
An offense that rarely turns the ball over, makes the opposing offenses have to gain more yardage and gives them fewer attempts to score.
An offense that can control the ball and put up a lot of points forces the other team's offense to take chances - leading to turnovers and sacks.
Knowing that your offense can score a lot of points leads to more aggressive defensive play from the players and play calling from the coaches - leading to more turnovers and sacks.
Good special teams also makes the offense have to gain more yardage to score.
Perhaps most important is the mental aspect. Pro football is rough, tough, marathon. Training camp, preseason, 16 games, it wears on you.There comes a point when many teams realize that they are not going to have a special season. At that point, the team starts to fall apart. Sure, they are professionals and they should play their hardest, but the fact is if you are in week 14, you have been eliminated from the playoffs, and your QB is Cassell/Moore etc. you are just not going to play as hard as you would if you are in a play off race.