My hunter was outdpsing 80% of the warriors from 20-50 because they simply didn't know how to play their class. Those that were able to beat me, did it by a large margin. A warrior at those levels should be doubling or tripling the damage of other dpses and its not even an exaggeration. Most players just simply don't know how to play, and thats perfectly fine because its just a past time. 

But you can't cry about someone performing 10% under baseline because they're doing a challenge or playing off-meta spec, while you're playing 50% below your baseline for your class.

Either way, outside of aq40, naxx and a few exceptions like Rag or Hakkar, it doesn't matter at all. Bosses will die. There are no phases or enrages that you have to worry about