Buffs and nerfs

Warcraft is not a static game. The rules change every few weeks/months. Some classes get stronger, some change, some get weaker. Recently Retribution Paladins got the nerf a bit. Before 3.2 a Retri opening would consist of Crusader Strike (lot of damage) Judgement (lot of damage) Divine Storm (lot of damage) - in PvP this meant that Paladins of this persuasion would literally blow people before they got a chance to do anything. Especially because all of those abilities are interspersed with auto-attack that also procced Seal damage.

It's changed now so that the Seal of choice needs a bit of time to get going and deliver a lot of damage. Crusader Strike now has a lower cooldown and also does less damage. In short the potential for huge bursts has been reduced, but overall the damage is still reasonable.
No matter what the changes are invariably people seem to dislike changes, or at least big changes like this. If something gets changed from 5% to 10% you don't hear anyone, but small tweaks like that are rare. Blizzard like big changes and a lot of them. So do I.

Lots of small changes that would slowly make everything creep towards something resembling balance is just not what Blizzard are after. They want you to have to deal with changing circumstances. Balance is not a realistic goal when some people wear cloth and others wear plate. Big kick-ass two-handers vs. wands.

I think almost every class has had one of those patches where people were declaring that Blizzard 'hated their class' and they were going to quit. Strangely Warcraft is still going strong and I can't think of any class at the moment that is really useless, unless played badly.

I've found that buffs and nerfs come in cycles, sometimes you're up, sometimes you're down. Blizzard seems to make decisions that make you grab your hair and want to pull it out in big clumps. I think their decisions are almost purposely made that way - again, they want you to deal with changes. The system must be unbalanced so new changes can be made.