Here's what I've see so far this playoffs:
Giants over Falcons - Two bottom-of-the pack defenses playing with the Falcon's actually being better during the season. The hot team won though.
Broncos over Steelers - Defensive scheming is just as important as defensive talent....
Saint's over Lions - No defense, better offense won. Moving on
Texans over Bengals - Average bengals team with a poor offense and rookie QB on the road against a stout defense.
Giants over Packers - Packers had the better defense and offense during the season, Giants were hot and the Packers weren't. Simple as that.
Ravens over Texans - Difference was Ravens offense. While not great or even good they were facing a team with practically no offense.
Pats over Broncos - Defense knew how to kill tebow, but really they just couldn't handle the offense.
49ers over Saints - It took the game of Alex Smith's life for the 49ers to scratch out a win against the high powered Saint's offense. Giving up 32 points isn't what I'd call a good defensive performance. The game is 60 minutes, not 45 or 50.
Giants over 49ers - The 9ers shot themselves in the foot but it really came down to the inability of Alex Smith and their offense to put points on the board. 17 points in Overtime? More often than not it's not going to be good enough no matter how good your defense is.
Pats over Ravens - Flacco and the Ravens offense couldn't make the plays to win the game and put up enough points despite Brady playing poorly and the Pats only scoring 23 points.
I'm not sure what playoffs you've been watching, but the teams I've seen win have been either the hot team or the team that could play complimentary sides of the ball, not the defensive juggernauts. Just because 2 of the highest scoring offenses get knocked out doesn't mean that "O LOOK, DEFENSE STILL WINS CHAMPIONSHIPS!!!!". It means A. their defense is that bad and/or B. They played a bad game.
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Why do people have a hard time with this. One unit in and of itself means nothing. Your greatest strength is only as good as your biggest weakness. Balance is the only thing that is important. I'm not talking about balance in terms of making each unit as good as the other. I'm talking about maximizing potential in terms of point differential. A team that gives up 50 points a game but scores 80 is a better team with more balance than one that gives up only 10 points but can only manage to score 25.
The Browns and Dolphins gave up the 5th and 6th least points this season. Must have been good, right? Combined 10 wins....
Look at the Baltimore Ravens. They only won one superbowl with their often league leading defense since 2000. Why? The offense. Guess which year the team had the highest point differential (and was 2nd in the league)? 2000.......
The difference between the 2005 and 2008 Superbowl Championship Steelers teams were the offense. Ranked 8th in '05 and 20th in '08. Guess what was the same? You bet, their 5th ranked point differential. Much better defense in '08 compensated for the worse offense.
Of course there's a lot more beyond point differential and you can't completely avoid the luck factor (see '07
)