It seems like a small change, but it could be the herald of something larger. It's a change to the way the defense skill is described in-game in patch 2.4.

  * Old value: Higher defense makes you harder to hit and makes monsters less likely to land a crushing blow.

  * New value: Higher defense improves your chance to dodge, parry, and block attacks, makes you harder to hit, and makes monsters less likely to land a critical strike against you.

    So what does this mean? They've added things that have always been part of the skill, but have not been explicitly mentioned on the defense tab before, but what's most intriguing is what they've taken away.

    One of the biggest ways a Paladin or Warrior knows they're ready for the big time in tanking is if they can completely remove the chance to be crushed by an enemy using gear, talents, and skills. One of the biggest complaints that Feral Druids have had is that they have no skill or talent (such as Shield Block or Holy Shield) to help them avoid crushing blows. It's a topic that's on the mind of every serious tank every time they go to any raid instance.

    The best money is on them waiting until WoTLK to completely do away with crushing blows. Level 80 should allow them to more easily balance out the four tank classes while taking the removal of what has been a rather dominant mechanic in many encounters up until this point into account. That said, it could still be starting now, with this seemingly innocuous change becoming the harbinger of a much larger change in the way we tank.