Edited the title so it didn't say 40 instead of 80
For your question it's hard to say. No one class really shines above the rest from what I've seen. I would suggest comparing some Wow Web Stats reports (Most people use patchwerk as a benchmark because no one is at a disadvantage). But there is no promises that the players are all equally geared/skilled. Also there are a lot of class changes in the next patch so it will change once that's released.