I’ve been tinkering with some stuff this expac, my focus has been looking into the relatively lesser supported things in the game or items that look underwhelming (missing a few items that I want to test out so that might need a different thread).
Things I have managed to notice so far are :-
1. Vitality Decay -
[spoiler]1. Lack of Vitality Decay duration sources -
Only one pistol provides me this stat, another thread here points out HoS exclusive aura is underwhelming and it was suggested there that bonus duration to the stat should be added
Besides that some constellations, armor pieces and jewellery with the stat is appreciated
2. Gearing for Vitality Decay builds -
Now I must’ve missed something but the Vitality Decay sources (when one disregards item support) that come to mind are - Corrupted Storm, Reaping Arc, HoS Aura, Second Rite, Entangling Vines, Drain Essence and Bone Harvest and Blood Boil
In my experience Drain Essence feels a little clunky for DoT based playstyle but that’s just me, I tried something with Ritualist and Bone Harvest, the lack of DoT sources really hurts despite Bone Harvest being excellent for DoT based builds
Corrupted Storm is a decent source and so is Entangling roots but the lack of duration really hurts
Some gear support for these skills in the vitality decay department is very much appreciated
3. Conversions and Skill mods-
Now, the things I haven’t tried with a Vitality Decay build is a DEE based VD build using Mythical Blood Orb of Chthon for Poison -> VD. That could work. Then there’s some oddly placed support for Vitality Decay in Phantasmal Blades
And something using Soldier’s Conduit based Blade Arc mod for physical to vitality
Then lastly there’s Decree of Malmouth and Conduit of Demolitionist for Vitality based BWC build
I haven’t tried the above but conversion while very much appreciated shouldn’t be the major point of defining a certain damage type’s strength and class skills that deal said damage type should be looked into and supported with apt gear
4. Relic -
Reaping Arc being melee locked isn’t very appreciated especially when I am stuck using a gun
I hope the melee locking is removed as it looks like a very good source for Vitality DoTs and would also encourage more builds around the skill itself
Not sure if a class skill is a good example here but when ABB’s weapon locking got removed it became a little more desirable choice for LMB slot. Reaping Arc looks good and it’d do wonders to build diversity to remove the melee lock.[/spoiler]
2. Legendary Acid/Poison Pistol and Cold Shield -
This is odd that we still lack any Cold shield. And the only Legendary pistol that fits the acid pistol theme is dealing Vitality damage. I hope you guys look into this.
I can see that Coven’s pistol is good for acid but I’d also like to see the addition of a legendary pistol.
And about the other thing all I can say is that considering we have Fire/Lightning shields, a cold shield not being here is perplexing
3. Drain Essence -
[spoiler]1. Item Dependency -
Drain Essence’s damage at ultimate max level is 3 times than that at max level. This is odd and makes the skill unappealing due to the extreme item dependency
2. Gravechill -
The modifier isn’t desirable at the moment. I tried it with a spellbinder since Arcanist offered the crit damage, energy management and cast speed I desired.
The removal of ADCtH on the transmuter forced me to get Mythical Vigar’s Hunger and Mythical Riftwarped Grasp to compensate for the lost ADCtH
The lack of RR on either masteries forced me to use Crescent Moon and Necrosis.
The modifier gutting the ADCtH is bad enough and to make matters worse the gear support being non-existant posed a very high problem. One set compensating for the lack of RR and the missing ADCtH might solve this[/spoiler]
The suggestions below are purely based on personal preference, do consider them though 
* Lack of Legendary Green Lightning -
Currently Aether Lightning is in a state similar to the pre-expac PRM procs which were restricted to greens and epics. At this point only legendary supports aether lightning
I personally would like to see more Aether Lightning themed procs
*. Final Superboss skills-
The final super boss of the game has two very appealing skills - the crystal fire forcewave type attack and a very cool Fire based Doom Bolt
I personally would love to see these on some items as procs or granted skills