I have played Havoc DH for 3 years and can confirm the current design has many, many issues and the spec has been neglected more than any other spec in the entire game.
Here are a few changes which would change the viability of DH in both PvE and PvP in terms of Single target damage, AoE cap damage and Defensives:
- 2nd talent on the top " Improved Chaos strike" is removed, 10% is given to Chaos strike baseline and the talent’s spot is taken by a choice node of Netherwalk / Desperate insticts is reworked into providing 2 charges of Blur. This allows for Havoc to be better at surviving.
- Chaos Theory talent is removed. Essence Break is moved to its spot up in the Tree, with the duration being increased to 7 seconds. A new talent for the most bottom left row is added “Insert name here” which either removes the target cap of all your abilities or at least increases the target cap by at least 3, and further reduces the cooldown of Metamorphosis by 30 seconds. This allows the player to have more meaningful burst damage.
- Mortal Dance talent is removed, Blade dance / Death Sweep receive a 25% in PvP (50 in PvE) antiheal effect baseline just like Rising Sun kick for Windwalkers and Mortal Strike for Warriors have been for many years. This is an outdated talent that shouldn’t exist anymore.
- Glimpse (PvP talent) retains the 35% damage reduction for 3 seconds after landing as well. The current iteration of the talent only provides the damage reduction during your time in the air, and generally that isn’t more than 2-3 seconds by itself even if you pre-double jump. The Death rate of Demon Hunter in PvP is much higher than any other Melee spec. This will help out Havoc Demon hunters survive longer against people who permanently try to kill them.
- Darkness’s becomes a 4 minute cooldown in PvP baseline. Choice node for it " Long Night " is reworked to the Darkness being where the Demon Hunter is (like an AoE Aura) so if you move, you move the AoE Darkness with you. Currently the spell is very clunky, with it oftentimes being completely ignored by people who don’t see it, or forces people who stand in it to overrate the value and die. This fixes multiple clunkyness issues with Darkness.
- Eye Beam becomes uninterruptable. Makes little sense for a Melee class to get hard countered on their signature spell by both Interrupts and CC at the same time. This makes more sense for a Melee class.
- Ragefire talent gets reworked - When your Immolation aura has done as much damage as your total health, the damage of Burning Wound is doubled for 15 seconds. This makes the talent choice viable - nobody is currently picking it in any form of content, especially with how deep the talent is.
This is my input. For a class which has only 1 DPS specialization, it is only fair that it receives attention.