Only Havoc is worthy of some critique here. Vengeance isn’t in need of anything being removed (like seriously, that class needs love).
Havoc DH is receiving a soft nerf in 9.0 in terms of its current performance due to it not getting any skills to unprune whereas I as a Ret Paladin can have baseline consecration while keeping wake of ashes.
Additionally if you actually have played one big damage is coming from Furious Gaze which appears to be designed to help both its ST and MT.
All they would need to do if they wanted to ‘nerf’ it is to make gearing in the coming expansion have the class choose between boosting ST and MT on havoc.