I do know that they changed the agility rating for warriors, like they did with the hunter class. Basically, you need about 26 points of agility for 1% crit come TBC, compared to about 20 now. I assume they've changed the other aspects agility affect as well. The item AC value buff could then possibly be similar to the ranged weapon dps buff, that is a balancing act to weigh up for the agility nerf, although I am wildly speculating here.
Penn of Nihilum-fame is being quite vocal about the changes in the EU warrior forum, as an example, see:
http://forums.wow-europe.com/thread....70397094&sid=1