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!
Another theory is that this buff is temporary, and it goes away in Phase 3 of the Isle of Quel'Danas progression. I'm not sure where this theory came from, possibly something from the PTR. It makes a little story sense, the strength of the mobs inside the raid weaken as their faction loses ground. Then again, you would think something in the event would mention that.
The third interesting theory is that this spell is Blizzard's way of being sure they can nerf the bosses quickly and easily if they decide it's tuned too difficult. Altering a spell or removing a spell may be easier than changing an entire encounter. Again, I don't think that this one is likely.
The first theory is the one that is probably the most likely. I don't think Blizzard likes Crushing Blows, and current itemization doesn't lend itself well to a world without Crushes. Certain tanks would become crazy, crazy powerful. We may see a removal of Crushing Blows in Wrath and a revamp of how tank gear is itemized. This lends itself well to Death Knight theorycrafting. Without the addition of a brand new mechanic to the class, Death Knights would have an incredibly hard time pushing Crushes off while Dual Wielding or Two Handing. Parry stacking for the win? This is most likely their attempt at seeing how a lack of Crushing Blows will work, while still making a raid zone difficult.
I don't mind it, to be honest. My raid's healers may disagree with me, but it doesn't seem like it would be substantially harder in all situations. The incoming damage will be higher, but probably more steady. The random insta-gib might be going the way of the Dwarven Mage, but we can't say for sure quite yet. After all, Kil'jaeden might hit our tank with a 35,000 damage Crush the moment we pull him, the first time we see him. Who knows?