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/9QuFYFG.png

Short summaries

NV Terra Decimates all other mages in burst damage, albeit not stepping on Physalis' or Ibara's toes in terms of elements. Even when compared to an Ibara with strong LB damage and killer buffs applied, you can expect Terra's LB to deal around 50% more damage; that number will change based on what you have available for each of them and what type of foe you're facing, but it's a promising figure for a unit with no external support beyond chaining. For foes that don't melt in a single LB, Terra has unremarkable chain damage. Despite this, she's still #1 in average damage thanks to the LB. Field effects are somewhat of a gimmick right now for squeezing out slightly more burst damage, but I'll be keeping them in mind for countering specific trials when relevant.

Great Mage Kefka The strongest non-limited NVA mage, hovering around Grim Lord Sakura's damage, but not looking particularly great with Terra opening the floodgates on magic damage. Kefka prefers lightning, but does ~85% as well in his base form with ice, or worse again with dark. 150% killer buffs are great for dark visions, but given they're restricted to 2 turns and 2 uses, they're not a massive game changer for trials. If you're patient enough to wait til turn 9 and spam his LB every other turn or so, Kefka's damage will improve, but only by about 10-20%.

Noting here that every one of Kefka's elemental CWA skills are AoE. If you're using him for killer buffs in dark visions, be aware that he'll either have to use his T CWA frames LB, Hyperdrive or CW frame skills if his initial damage is going to kill enemies, lest his subsequent casts get cancelled. Fair game for a literal clown to prank you.

Assassin Shadow Debuffer/chainer archetype like Loren, though having similar damage to her is pretty tame now. Assassin Shadow has a slightly lower full break at 80%, but also boasts AoE mirage, provoke (with a respectable 40% passive evasion), 84% DEF break on turn 2, and a katana imperil to boot. While not an outright replacement for either of them, Assassin Shadow falls somewhere between Loren and Seeker of Freedom Vaan in terms of kit.

NV Locke Another kind of weird damage dealer/breaker akin to Onion Knight, leaning more on the breaker side. Locke's base form has weaker damage overall, and a fairly typical breaker kit, though he does have 1 turn downtime on his 85% full break. 90% ATK/MAG break on an LB is a new high, though at 2 turns and 42 LS cost, it isn't exactly guaranteed without support, and the jump from 85% to 90% breaks is nowhere near as pronounced as it would be in the past, with recent bosses having passives exceeding 60%. Provoke on a high passive evasion breaker is nice for those lacking draw gear, though the massive self bird/dragon mitigation is irrelevant for the time being. The trio of weapon imperils are a nice bit of a utility on a breaker that sorely needed something unique.

Shift form keeps the provoke and weapon imperils, but mostly sticks to being a typical T SR fire chainer with unique frame LB. Magnus finisher for removing buffs is nice, as are his bird killer buff and AoE fire imbue chain. For context on damage, Locke's falls pretty squarely around Onion Knight, Riku, and Sora's; however, he doesn't scale up in longer fights like Onion Knight does, and he doesn't have big burst damage like Riku and Sora do.

Fighter Sabin As a mage in his shift form, Monk Sabin of Kolts spamming CWA is either doing mediocre damage near the bottom of the NVA mage list with light damage (~73% of Kefka's damage), or losing to 7* mages with fire or wind damage. The modifier on his LB actually compensates for it being non-elemental damage, to the point where Sabin LBing every other turn would be outdoing Kefka by almost 20%; however, no LB passives or fill skills in his shift kit make this somewhat annoying to pull off, though his base form's LB support can help on some turns. Additionally, many trials arbitrarily resist non-elemental damage. For a lot of content, Sabin is simply going to be an underperforming mage who happens to have >20k HP.

Sabin's base form deals less damage overall, and is overall annoying to deal with (can't W skill his LB upgrade and LB damage buff in the same turn, imperil skills are different chain families to his primary damage chain). Sabin's real unique characteristic comes into play with his access to 5 turn covers for both physical and magic damage respectively, allowing him to even switch into his other form and deal magic damage if desired; this is only really practical on ancient content, or where you can exploit evasion or elemental resistance. However, wouldn't you rather do literally anything else? I'm sure Sabin is usable in trials with these conditions, but his added value is going to be fairly negligible over dedicated tanks regardless.

King Edgar Not ranking him since he's a dedicated finisher, but worth mentioning for context that King Edgar of Figaro's burst damage should be ~15-20% higher than Sora or Riku's. Due to the setup turns and time in the air, average damage is more in line with an older NVA like Pyro Glacial Lasswell however.

Eldryn (Eldryn's icon isn't working right now) Mixing feelings overall. As an ice-locked hybrid chainer in his shift form, Eldryn is outpacing Sora and Riku's damage by about 15-25%, but is lacking in burst damage. Elemental absorption is good to have, as is his respectable 1 turn 80% break magnus. HP drain counters keep him healthy, though it's unlikely for you to be in a situation where only Eldryn would have been in need of healing after an enemy.

The base form is where things get weird. Eldryn has no imbue in either of his forms, and nothing here is elemental, which does mean he isn't hard ice-locked. However, he is weaker in this form, and even weaker still if you choose not to upgrade Sabre Assault, which forces him to physically cover for a turn. He is bulky for a chainer, but nowhere near tank levels. Even in the cases where his 10 stack mirage is a viable solution (and it will get eaten up fast by AoEs), it's limited to 3 uses, and he can't use his LB to keep 10 stacks up while covering. I don't know really know how Gumi intended for him to be used defensively... LB mirage lasts multiple turns, so you could theoretically rotate between a pair of Eldryns switching between chaining with someone else plus covering, then LBing for mirage setup. It really does sound like more trouble than it's worth for a strategy that gets shut down by AoEs. Regardless, uh, he's a strong mostly-ice-locked chainer with some global weirdness going on.

Christine Christine kind of got the short end of the stick this year, so I'm officially declaring it canon that Kryla successfully stole her soul, and everyone with NVA Christine is simply commanding her remaining husk of a body around. Plot aside, Christine is effectively dupe only now as nobody else relevant uses quad AZ, and they definitely won't use quad AZ and Extreme Nova in a loop. Christine does have the option of granting quad AZ to a tank or support or something and then having Xon chain with her for the LB, but that's about it in terms of viable non-dupe partners. Her damage is relatively strong for an NVA mage, at ~25% stronger than Grim Lord Sakura. However, her hard ice lock, restrictive frames, lack of utility and one killer buff compared to Sakura's two elements (and any imbued), common frames, three killer buffs, and further utility mean that I'm pretty comfortable putting Christine below Sakura. In regard's to her base form, Christine would mainly be using it for the AoE 15% ice boost, and maybe playing chain partner with her old weak CWA skill or ice finisher.

ヽ(￣～￣ )ノ

A bit wordier overall this time, and with numbers! Let me know if you prefer this kind of analysis, or would rather I stick to a single paragraph when possible.