The traits I would recommend for this scenario:
treacherous covenant - currently the best siming trait for both ST and AoE.
The reason behind it lies with passive agility bonus, which is (and should be) available at the majority of time. You gain pasive agility which increases your attacks both at ST and AoE => agility is your best stat. The more you got through anything (food, flask, rune, traits). the better.
I would stack this traits as much as you are able.
Furious gaze - Why? Because it increases your haste after channeling, haste can be used to cast blade dance/death sweep more often. While also reducing your global CD to cast demon’s bite and chaos strike/annihilation more often. From my experience each furious gaze gives you around 15% haste after you let it proc. It is up to you how many of them you will stack, but at least one of these is nice to have.
Chaotic transformation My favourite trait. It completely changes your opening rotation. It gives you 2 eyebeams at your opener. More deathsweeps/blade dances. Eye beam is your best ST and AoE skill. So the more you have available the more bursty you are. It is must have trait for m+ where you can zerg the reaping pretty much easily with this trait. This trait is not good for stacking, because the effect aside from added demon’s bite damage cannot stack.
Then you can add one thirsting blade to boost you ST (the more you pick the more ST you get, but keep in mind that this trait is strictly for ST scenarios. One is however not bad to have at your disposal.)
For boosting your AoE you can add revolving blades (these are however not good for ST (same as thirsting blades are not good for AoE)
That would be your first two rings.
The third ring really depands… For example good AoE trait is Azerite globules. Good ST is guntripper.
The main thought there should be balance => get few AoE and few ST traits
The survivalbility ring is based on your preferences and what you find the best. It mostly doesn’t change your DPS in any way. Basicaly you just pick what suits you.
That is for traits. Now to talents:
Demonic build is currently the best for both scenarios. You need to pick blind fury for your first talent and demonic as your last for it to work. Then I reccomend picking imolation aura (good for fury generation and AoE). Definitely take first blood - other talents are trash at this tier.
But the main decision lies between fel barrage and trail of ruin (ToR).
ToR is good for both ST and AoE. However in certain scenarios the fel barrage might be better as it adds a ton of AoE burst which is often needed (especially at m+ in certain affixes. But if you are starting with DH - ToR is the safest pick - it is also better for what you want (have good ST while also keeping good AoE)
If you have other questions regarding to your gear or what talent, trait to pick - you can always head to raidbots - which is the site that sims your gear and finds you the best combination. But keep in mind, that it represents ideal situation at ideal conditions => it is good to give you a direction but always use rather your brain when you are deciding which way you will take.
I can also reccomend you a good DH channel where you can find a lots of guides for havoc, regularly updated with patch notes: TaylorMade_TV