I try to keep class balancing in an expansion and content in that expansion strictly seperate. I don't have to be negative about the expansion when it's my class that's the problem, and not the content.
That said, there were posters warning that there would be problems with the mana removal back when they did it, and it was waved away. If it is indeed a problem we'll find out soon enough.
With all this it is actually an advantage that raids open so late. That means Blizz will have ample data & time to make sure all the classes are up to date before things get serious.