As far my close and personal friend Illidan goes, he will no longer be casting Shear. While I understand the need for this, as a Warrior can no longer spam Shield Block come patch 3.0.2, I will miss this particular mechanic in that it truly provided a test of skill above the standard tank and spank mechanic.
The HP nerf to all of the raid bosses isn't sitting too well with me either. It makes me sigh in frustration at the weeks my guild spent getting the last 25% of Brut down to a science. Had this nerf been in place three months ago, we would have killed him on the second night of attempts.
But that is the life of these games, onward and upward towards Wrath of the Lich King!