Here I will give some more detailed opinions on the different soulbinds and covenant options.
If you are just interested in the sim dps of each soulbind skip to the charts
She is a healing soulbind. Skip
Forgelite Prime Mikanikos:
Finally a good soulbind for Kyrian. Bron’s Call To Action can be a nice form of CC especially in M+. In raids it might be a bad thing to accidentially cc targets that are supposed to be moved. It also deals pretty good damage. Additionally Hammer Of Genesis grants you 3% Haste for 10 seconds whenever you damage a new target, which can be incredibly strong on encounters with add waves.
Pick Forgelite in pretty much all cases.
Plague Deviser Marileth:
The worst Necrolord Soulbind. Plaguey’s Preemptive Strike is the only ability in this tree that actually affects your damage by increasing the damage done to a new target by 10% for 10 seconds. Sadly Elemental doesn’t have a very good single target burst, so it falls behind the alternatives.
Even after the Nerf Emeni is propably one of the best soulbinds in the game. If Lead By Example affects 4 other people, it elevates her to the best soulbind in general. Gnashing Chompers is sadly not that easily simmed but will likely be worse than the additional potency conduit.
Heirmir is the alternative if Emeni isn’t consistently affecting enough friendlies in a fight. Heirmir’s Arsenal: Marrowed Gemstone is incredibly strong in AoE and mythic+. In addition to all of this Heirmir can run 2 Defensive and 1 Utility Conduit while running the highest possible damage path. On top of all of this might enable you to clutch a kill, especially with it being able to proc twice after using Reincarnation.
Pick Emeni when you haven’t unlocked Heirmir’s Arsenal: Marrowed Gemstone yet.
After that pick Heirmir in M+ and when not able to consistently get 4 stacks on Lead By Example.
Nadjia The Mistblade:
Thrill Seeker is potentially a very strong ability on some of the raid fights in Nathria, with frequent add waves. We are gonna have to keep an eye on uptime on this one. Dauntless Duelist is on the contrary build for single target fights.
Theotar The Mad Duke:
Soothing Shade gives us mastery. Meh Wasteland Propriety gives us and 4 nearby allies versatility. Not entirely bad but it does cost us a Potency slot. All in all Theotar is subpar and doesn’t offer anything interesting.
Built For War sims relatively well but will perform far worse in most types of relevant content. All in all Draven is a tank soulbind. Skip
Overall Nadjia is propably the best out of the Venthyr soulbinds.
Niya is an incredibly potent soulbind. It is the highest simming across all covenants in single target, because Niya’s Tools: Burrs is just that powerful. Sadly this only becomes available with the full tree unlocked.
An interesting soulbind in that it is the only one that has two potency conduits unlocked in week 4. Field Of Blossom isn’t bad in AoE but get’s outshone by Korayn.
The highest skill cap soulbind. Wild Hunt Tactics is incredibly potent dps-wise, but because most fights become progressively harder, in practice it’s slightly worse than sims would indicate. First Strike grants 25% crit chance for 5 sec after damaging a new target that hasn’t damaged you before. This can be heavily abused in m+ by chain pulling new small mobs on top of a big main target. Because EQ is not target capped we do not profit as much off of it as other specs do though.
Dreamweaver while it gives you an extra potency conduit.
Korayn for mythic+ and raids with waves of adds.
Niya for single target.