Not sure what you are passing that on.
Yards/Game 2011 2012
Total 308.2 275.5
Rushing 77.3 90.8
Passing 230.9 184.7
Points/Game 14.3 14.2
Compared to last year, our defense is allowing less yards per game. The only weakness is being slightly worse at stopping the rush, but more than making up for it in stopping the pass.
Furthermore, compared to last year, we are playing a much tougher schedule and playing in one of the best divisions (although to be fair, we have three other defensive teams in our division, not offensive powerhouses) instead one of the worst divisions, so no question that our defense is better this year than last.
And yes, knock out hits are rare. Obviously if we were knocking out running backs and receivers every game the NFL would probably have to modify the rules, because concussions are serious business. However, the hit was not a fluke. It was the type of hard hitting tackles our guys do, so a few KOs a year are expected the same way that the turnovers were expected due to Brees airing out the ball.