Think it's obvious tbh.
Majority of DH's don't know/care how to play DH.
The few that do can't compete in itemlevel (700 vs 745 ánd not having access to all talents).
I am doing 200-500% more dmg than DH's and my wife was in a near 100% DH raid that could not even kill an invasion boss...
Which is logical since they are new and balanced around 110.
Would you want such randoms in your group? We carried our guild DH through HFC mythic and think he even got tierx4, but he is still way behind in dps because he does not have acces to all talents yet (only 2 tiers). Don't expect much from DH's in Pre-Patch, it is not their time yet.