Any system that makes non-winners eligible for the playoffs isn't good for pennant races, but the argument MLB makes is that two wild cards may actually be better for pennant races than one. By forcing the two wild-cards into a "play-in" round, it screws up their rotation and creates a greater disadvantage for being a wild card, thus encouraging teams to play for the division win rather than "a playoff spot," the argument goes.
The problem is that had this system been in place this season, the excitement we saw on the last day of the season as the Cardinals and Rays defeated the Braves and Red Sox for the wild-card spots would not have occurred, since all four teams would already have been in. So instead of an exciting, climactic night of baseball,we'd have an anticlimactic night of playing out the string as the teams prepared themselves for the wild-card play-in. But the powers that be in baseball don't see that.
You are right about 2011, but all the planets had to line up for last years race to occur. If you factor in the other years’ races, then this new system might make sense.