https://exvius.gamepedia.com/Chainer_Rankings_by_Suede

If icons or unit names aren't displaying properly for you in this thread: https://i.imgur.com/7NGqOia.png

Short summaries

NV Gabranth While it's not fair to consider Gabranth in the same way as dedicated chainers, he's doing around 2/3 of a decent chainer's damage while keeping provoke up. Not great, but meaningful. Unfortunately, his damage comes from the shift form which can't AoE cover, but I think the addition of imperils and AoE 45% physical mitigation is helpful enough, given that a provoker mediocre damage dealer isn't a particularly desirable role on its own currently.

Balthier Another merely okay NVA chainer. Prefers lightning, but can also imbue water, fire or light. Passive bird and beast killers are nice, but without active ones to steal, Balthier lacks the niche that units like Red XIII can fulfill in spite of their damage.

(CG) NV Firion Strong across the board, with diverse killers being the icing on the cake. Due to his base form being better at chaining and the shift being better at finishing with his LB, Firion can get a lot of mileage out of stacking his shift form with LB damage for burst turns without jeopardising his chain damage; the ability to grant the Wild Rose chain to the party from a setup action makes it that much easier to accomplish this. Also of note is that a pair of Firions chaining Blood Weapon most turns will heal 72% of the team's HP, taking pressure off your healer so they can do other impactful things with confidence. I typically wouldn't consider dropping a healer when running Firion, since healer kits are so loaded and Firion needs to spend some actions on setup for himself.

Dark Knight Leon One of the stronger NVA units like Pyro Glacial Lasswell. In Lasswell's case, he was offset by a heavy incentive to use ice only, including ice only burst damage. In Dark Knight Leon's case, he isn't as penalised for using a different element, but his auto-casting chains mean he benefits from being run with a dupe. Additionally, he lacks burst damage, and his shift form's only real use is for an underwhelming 50% spirit killer buff and emergency self HP/MP sustain; it's an outright damage loss compared to his base form due to the missing 6x chain cap. Regardless of his quirks and janky design, Leon is undoubtedly pretty good for an old unit.

NV Madam Edel Powerful unit with a high ceiling. Like the old Edel, NV Edel takes a whole damn 12 turns to get all of her mod boosts online. Her damage across her opening 6 turns puts her in the realm of typically strong chainers like remake Cloud and Akstar (who admittedly also ramps up), while a fight extending out to the full 12 turns makes her the outright strongest chainer. For fights longer than 12 turns, she's going to outdo units that aren't released yet. The caveat as always is that she's punished hard for dying, and trials at this point in the game aren't typically lasting 12 turns. Despite this, NV Edel performs well enough on short fights, and if you play methodically, you can take advantage of high burst turns too. Small note that her base form has some obvious uses in dark visions due to the elemental damage boosts, but in trial situations against non-stone foes, she'll want to LB for the mod boost and stay in shift ASAP.

Nal Personally surprised me a bit with her damage; Nalu is among the particularly good NVA chainers (Leon, Lasswell, Loren). She is more or less lightning locked, but with a 130% imperil, 100% self beast killer buff and targetable LB damage boost, Nalu is more than pulling her weight. Just make sure you're sticking with Dark Gandiva, Sagittarius or Firion's Bow as Vajrayana's 1.25x variance is a sizeable penalty to her damage, and the spear passive doesn't make up for it.

Dangerous Ariana (Ibara unit icon isn't available yet, /u/Nazta pls update 💖) Ibara is the first actual dedicated NV magic chainer, so she's obviously the strongest. She's pretty straightforward as a quad CWA chainer who has nice self human/spirit killer buffs and a powerful LB finisher to boot. A potential issue for her is that purely dark damage (as opposed to lightning/dark) is only available in her brave shift, which is a big problem given its 5 turn duration and 5 turn cooldown; hopefully we won't be seeing too many foes that are neutral or susceptible to dark that resist or negate lightning.

The biggest question surrounding Ibara now is whether the bug affecting some magic skills will continue to affect her. Pandora's box has well and truly opened by now, so I'm making no effort to pretend the bug doesn't exist. If I'm understanding correctly, it's almost a 50% damage increase on a unit that absolutely does not need it, so I wouldn't expect it to stick. In any case, I'll keep my eyes on it. As of today, she's #1 by a wide margin even without the bug.

Grim Lord Sakura 3spooky5me. As a quad CWA chainer who prefers dark, Grim Lord Sakura is an easy answer for people who want someone to chain with Ibara in dark visions. Further cementing her DV value are her three self 150% killer buffs and three available elements to imbue, in addition to a physical type BS chain. For trial usage, her raw damage isn't bad at all, giving Aerith a run for her money. Sakura doesn't really have enough going for her as a dedicated support; her base form is also considerably weaker than her shift, and the majority of her support skills being on a separate multicast hurts her damage output further. Still, it's nice to have the option of stop prevention, break removal, elemental resistance buffs and even AoE reraise 50% mitigation in a pinch.

Lucius Gumi giveth, and Gumi taketh away. Lucius is the decidedly less potent of the NVA units this Halloween. Full breaking is nice, but at AoE 80% on LB and ST 75% on demand, he's already falling short of Loren in both break strength and availability. Raw damage for fire and dark elements is decent, but he's more of a Balthier than a Nalu in that regard. AoE imbues locked behind setup and two self 100% killer buffs tied to a magnus chain give him some clear uses in dark visions, though not nearly as appealing as Grim Lord Sakura. HP absorption passively is cute, but it doesn't really make up for anything aside from negating HP sacrifice skills.

ヽ(￣～￣ )ノ

As usual, let me know what you think.