I've been playing since vanilla and there have been ups and downs but nothing so drastic that it ruins the game. The class has changed but it has never stayed the same for a very long period of time.
I don't see any reason to be upset because I've never harbored any expectation of consistency over time concerning class design. Blizzard is constantly trying to improve things. As they are not perfect people we cannot expect a perfect design. Sometimes they over-correct a little too far left and then a little too far right the following time. I believe this is ok.
I can understand being upset if I were in a top 2% of raiding guilds in the world. Then again, if that was the case I'd likely not be as attached to a particular class as I am now.