Because lord knows that there were MASS Warlocks abusing every other class in the game. Jesus Christ that fuckin blows huge brontosaurus balls. Let me see if I can make a D2 analogy to explain the situation a little better.

It seems like everyone is murdering muthafuckers with hammerdin builds. Hammerdins builds are 5 out of the top 10 level characters on the ladder (probably not accurate on this but you get the point). The build is so dominant that you seriously cannot join a game with more than 2 players and 1 not be a hammerdin. Meanwhile the highest-level druid on the ladder is ranked 40th overall and 12 levels from the top spot. Those fucking Druids are too powerful… NERF. End of story.