WoW can't be fun for everyone all the time. By the very nature of arenas, one team wins and one team loses. Winning is fun, but losing sucks. So that means that 50% of the people in each match aren't having fun. Welcome to arenas. No matter how "fair" you make it, someone always loses.
If you really have no fun every time you lose, then I feel sorry for you and then I wonder why you are still playing this game. This doesn't only count for arenas in wow but also for sports in real life or any game people play. I don't know if you realise it but some people can still have fun playing a game if they don't win. If not then a lot of sports/games and stuff like that wouldn't even exist. Do you really think people would for example spend an hour of their time playing a match of soccer when there's a 50% they will not enjoy it, at all? I don't think so.
I myself, and I know a lot of people who share my opinion, enjoy a game whenever there is competition and you have a chance to win and a chance to lose. However there is no fun in losing a game without having any chance to win at all, just like it's not a lot of fun if you win while there is no chance you can ever lose.
Of course there will always be teams who have an advantage over you but Blizzard is trying to keep these advantages low. It's called balance.
Are you saying you think its fine if some classes are simply your anti class and you have no chance to ever beat them, and Blizzard doesn't do anything about it? You would just have to be lucky to win an arena game without any skill involved. But of course that is fine, because you can still win 50% of your games.