This existence of this buff was hotly debated at first, but analysis of boss attempts and long nights of fighting in the Plateau have mostly proven it to be true. There are a few theories as to why this buff exists, the most likely being that it is a band-aid on a gearing issue as they move away from Crushing Blows. As far as I know, nothing in the raid dungeon can land a Crush. If I understand Druid tank mechanics correctly(and there's a chance I don't), removing Crushing Blows would make them nearly unbreakable. However, removing Crushing Blows and implementing this buff is decent enough way to put a band-aid on something they want to move away from before they're able to make sweeping changes in Wrath of the Lich King. There's a net increase in damage taken, but it isn't as massive as it sounds. Bosses are still being killed.
If you're interested in this little(big) buff(nerf?), take a look behind the cut!