Don't know if anyone is still interested in this game, I gonna write about the units gameplay wise (based mostly on NG completely, only mandatory missions to get playable units faster so they gain Runes too from optional maps):
Elballad, 9/10 Auto deploy + free summon (Nick is Fire):
Main character that is deployed all maps, your starting mana is determined by his, so extra +Mana passive are useful to put on him to increase your starting mana each map. He also gains the ability to summon Nick at the start of C4 for free who shares Elballad's lvl and at lvl 20 you unlock a map that rewards you with 2 extra forms for Nick, so it's recommended to prioritize early boss kills for Elballad as they often only give Runes to the one landing the finishing blow so you can lvl up Elballad + Nick faster. Nick is also a Fire element, which deals full dmg to Undead.
Lavirie, 8/10 Auto deploy (Wind):
One of the two Main Heroines and auto deployed on almost all maps for the 1st time (not on repeats). She is also the 2nd cheapest unit to deploy at only 2 Mana. She is Wind Type allowing her to deal full dmg to Artifact enemies.
Has a lot of room for Reactive skills like Counter + Stamina Drain/Absorb allowing her to frontline well.
Pierce is also great to ignore shield.
On first visit, Lavirie adds extra starting mana if you equip +Mana Godmedal passive, but Lavirie only has 2 slots, so she might not have room for it, especially if you want to increase her base 3 movement.
Mistoria, 8/10 Auto deploy:
The other Main Heroines and also auto deployed on almost all maps for the 1st time. She is the 3rd cheapest unit to deploy at only 3 Mana. She attacks from 2-4 spaces away, but can't move and attack, she also has 4 move compared to most early units having 3, allowing her to keep pace.
Snipe is very useful against bosses as it forces them to stop and skip that turn if they move inside Mistoria's range.
Fan slap is a recommended Godmedal to equip, since it's a cheap to equip for 1 and cost 0 mana to use, allowing her to deal damage while moving and another ally to land the finishing blow.
On first visit, Mistoria adds extra starting mana if you equip +Mana Godmedal passive, she has 3 passive slots and good enough base movement that she can fit 1 or 2 pretty easily.
Nekol 5/10 Early game filler/cheap scout (Wind):
The first extra recruit. Since she joins early and also the 4th cheapest unit at 5 mana, she has a lot of opportunities to be deployed throughout your 1st playthrough. She can dodgetank single enemies early with Concentrate + Evasion Up, especially against low accuracy enemies. Being wind allows her to deal full dmg to Artefact, although her dmg output isn't as good as the other Wind units. She has 5 move and 3 Jump allowing her to be a useful scout after you cleared the initial enemies.
Forunisgein 4/10 Early Game Filler/Water movement :
Another early joining unit and the first with Water movement. Biggest drawbacks are that she only has 2 movement, 1 Jump, which means she really wants the Move +1 you can find in a chest from the Troll map you fight early with Koridora.
She can tank pretty well early with her unique shell shields and being the first unit able to move through water, let's her be useful in the early Water maps before you get any flying units.
She is also fairly expensive at 8 Mana, which means she is rarely deployed once better units join with similar cost and falls off once you get Gu-Landio/Kalima etc.
Rishe 6/10 Early-midgame healer:
Rishe is the 5th cheapest unit to deploy at 6 mana and she can heal allies for 0 mana. The first skill heals an ally +50 hp and later unlocks an 30 HP AoE heal, both are 1 use and has to be refueled by her skill that needs to hit an enemy, so it's a bit awkward sometimes. She is very useful early/mid since 30-50 hp is a substantial amount, but she falls off once frontliners become more self sustainable with Stamina Absorb/Drain and obsoletes Rishe.
Patra 5/10 Early Magic User/mid-lategame Scout:
Initially, she can't fly until you finish her events that unlocks her passive enabling flight.
So she starts off pretty bad with low atk, but can still fight using Magic that will be useful against Ghosts that take 1 dmg from physical attacks. Once she gains the ability to fly, she is the cheapest flying unit at 7 mana, allowing her to be a useful scout that can traverse any tile.
Gu-Landio 7/10 Early game Powerhouse but falls off later (Fire):
He joins at a high lvl relative to his join time (lvl 12, when previous units join lvl 7 and Kalema after joins lvl 9) He is Fire element to fight more effectively against Undead. He can stack a lot of early Godmedals, especially the Double Kill Godmedal he comes with, combined with 5 move allowing him to do a lot of work early. As the game goes on, better units join and Gu-Landio's 8 Mana cost is harder to justify, especially when one of your main Trio catches up his lvl and replicate his Godmedal build but for basically 0 mana to deploy. Still if you can afford the mana after deploying all the units better than him, he can still see use.
Kalema 6/10 Early game Wind DPS + Tank (Wind)
Another Wind unit, but the first one that joins at a high enough lvl to equip Pierce, which let's her one shot Gargoyles and nearly OHKO Golems. It's highly recommended you buy Pierce from the shop and equip it to Kalema for the Tower that unlocks Tsumugi in Chapter 3 as it's otherwise very difficult to deal with them thanks to their shield + Artefact that reduce all non-wind dmg by 75%. She also comes with unique armor to tank pretty well.
Biggest drawback is costing 8 mana and 1 jump 3 movement, so she will be outclassed (often by Gu-Landio/Tsumugi) when Mana is still limited, unless there are Artefact enemies to fight (Mezarbo's joining as a guest map for example she becomes relevant against).
Tsumugi 8/10 deploy 2-3 units for price of only 7 mana (White Shikigami is Wind):
Tsumugi on her own isn't that strong, but she can summon Black Shikigami for free, who can tank with Artefact skill vs Non wind/Non Peerless enemies, reducing Non-wind dmg by 75% and Tsumugi can later also summon White Shikigami, which lets you deploy a total of 3 units for the price of Tsumigi's 7 mana. She is a very economical unit only outdone by the main trio (can't be more economical than free).
Ardorkufel: 5/10 pay 9 mana to get Mistoria with +1 range and (Wind):
Ardorkufel is basically Mistoria with +1 range and Wind element, but you pay 9 mana for it, making him the most expensive unit for his join time. It's really hard to justify his cost, when his dmg is worse than Mistoria, except vs Artefacts who is either free or only 3 mana.
He is good against single bosses thanks to Snipe, but those are cheesed easily even without Ardorkufel.
(He is really good against Girl Gun Dolls, always countering them, but those are NG+ only for a small fraction, and therefore irrelevant)
Glarissa 6/10 BiS against Ghost only (Fire)
The only unit in the game that deals full dmg against Ghost enemies with Physical attacks. She is the MVP in any map with Ghost by equipping Counter + Stamina Drain/Absorb and sweep a group of Ghost.
Outside of this, she is nothing special, only 3 move and average dmg for her 7 cost, so there are better units to deploy if there are no Ghost to fight.
Noelia 9/10 First Flying Sweeper (Wind)
The first flier to join and also the next cheapest at 8 mana (only Patra is cheaper after she gains flight).
She has good mixed offense stats hitting either physical or magical very well, flight traverses any terrain with 4 movement.
A useful early magic build is Equipping -1 Mana cost x2, Double Kill and Black Ignition Godmedals and she can spam Black Ignition for 0 mana which is great to thin out a group of enemies for the upcoming crowded maps like Allargand's 1st map or the last mission of Chapter 5.
Princheno 2/10 water/ice map "specialist":
Has one of the worst stats in the game (to put in perspective her physical atk is lower than Rishe, her magic is on par with the likes of Gu-Landio on NG) on top of that, she has movement penalty on Land, forcing her to equip Land Adaption on most maps to keep up with your team. Her unique skill allows her to freeze the terrain she moves on, but most units have a penalty on moving on Ice, so she is rarely useful to deploy for 7 mana. She can walk on Water/ice with no penalty with 4 move 1 jump, but her stats are so bad that it's better to deploy a good unit with Snow/Water Adaption.
She is the 2nd worst unit IMO.
Allargand 3/10 joins too late to be useful:
He has very high hp and str, but only 3 move, 1 jump for 9 mana cost.
At this point, you can already have Noelia recruited before him, who is cheaper, flies, +1 move and nearly similar dmg output (or better with the magic Build) even without Noelia, Gu-Landio has better movement, Kalema has a special shield to tank better + Wind element, Tsumugi summons extra units etc.
Mezarbo 8/10 pay 10 mana for the price of 2-3 units (both summons are Fire)
Similar to Tsumugi, Mezarbo allows you to summon a unit for free, you can unlock his 2nd summonable unit later.
Both his summons are Fire, dealing full dmg to Undead. Being undead himself,, he (and his summons) take halve dmg from Non Fire/Non Peerless enemies, letting him tank them very well.
One downside is that both Tsumugi and Mezarbo start to hit your 9 unit limit on a map, so I recommend only fielding one of the two. Mezarbo deals better dmg, while Tsumugi is cheaper and 2 jump vs Mezarbo's 1.
They tank different enemies better, Tsumugi tanks anything but Wind and Mezarbo tanks anything but fire.
Elgamisera 6/10 flying magic Ghost tank.
Being a Ghost, she takes only 1 dmg from Non Peerless physical attacks, any enemy with no Magic (or a blind spot) are easily tanked by her and she can replicate Noelia's Magic build above. She flies and cost 9 mana, her drawback is 2 movement, but that is easily fixed with a Godmedal that boost movement (it's easier to fix movement than to fix terrain + jump)
Lutriche 4/10 Expensive:
She is one of the most expensive units to deploy at 12 mana and all you get is a unit with 3 movement with at least partial movement on all terrain, but she actually can't traverse maps as well as fliers, because it's she only has 2 jump and halved movement on Water/Air/Lava. It makes her inferior to actual fliers like Noelia and later Forzaslein and Riwo.
She has Artefact, but so has both of Tsumugi's summon, which is 3 units for nearly half the mana cost.
She has a very low ceiling, when she can only equip 2 passive and 2 reactive Godmedals (the lowest in the game tied with Rishe). Both her unique skills are way too situational, one repairs shield and one returns all item uses, both can only be used once per deploy. Both Shields and Items start to be less relevant as the game goes on and units sustain themself with Stamina Drain/Absorb and it's rare that you need to double your item/shield uses.
Lutriche is way to expensive for what she provides.
Forzaslein 10/10 Best unit (Wind):
Probably the best unit in the game. She flies with 5 movement, Wind type and high stats.
She has the best Godmedal composition, able to equip 4 Reactive skills and 3 Passives.
You can stack multiple Stamina Absorb/Drain + Counter and just sweep maps, in the Ganaf Jungle Mission in Chapter 7 for example, she can completely clear the physical enemy side and the boss all on her own with that setup even on Hard mode NG. On top of that she has an unique Reactive skill that prevents the revival of Zombies she kills.
The only drawback is her 13 mana cost (3rd highest) but it;s well worth it for a unit that clears maps very easily.
Koridora 4/10 Magic is not everything
Koridora on NG has the highest magic dmg output, unfortunately magic isn't that good in this game without a specialized magic Godmedal setup and you don't have enough Godmedals to make two of those builds. Elgamisera is usually better thanks to flying + near immunity to physical attacks for the same 9 mana cost to deploy either.
There are way too many unit you wanna deploy before Koridora, especially Forzaslein that joins at the same time.
Ageha 2/10 Expensive Water/Ice "specialist"
Very similar to Princheno, but more expensive at 11 mana. Same problems of needing Land Adaption to move in most maps that are often land based. Her stats are also extremely bad (lower atk than Rishe, Mag nearly on par with Elballad), especially for her cost, making her the 2nd worst unit in the game IMO.
Galanis Guardian 0/10, you have an easier time traversing maps with a wheelchair
Soooooo........ 15 cost is the most expensive unit in the game, you can't deploy him unless the terrain is nearly flat with enough room to deploy this giant unit. He can't even move and attack in the same turn, he can't traverse most maps due to his size, he absolutely needs Teleport and then he is sitting duck as he can't attack on the same turn as he moves.
Deploying this useless tank is such a waste of mana, just deploy ranged units with Snipe and you have much better success staying alive, especially against Riwo or other bosses.
Did I mention he cannot move and attack in the same turn if he is lucky enough to be able to even move by the way? Why would we spend 15 mana on a unit that can't move and attack in the same turn or sometimes even unable to move or be deployed at all on maps?
Riwo 9/10, slightly worse Forzaslein, still worth deploying (Fire):
Almost like Forzaslein but cost +1 more (2nd most expensive unit in the game) and -1 less movement. Fire is often worse element than Wind, since dealing full dmg vs undead is less important than Artefact enemies (it's only 50% reduction vs Artefact 75%). Upside is that she has full movement over Lava and deals higher dmg on NG. Deploying both is really worth it if you can afford their Mana cost to easily sweep the rest of the game.
NG+ ONLY (No real rating, since they are NG+ exclusive, but I will give my thoughts)
Eushully-Chan, would be a 10/10 if she wasn't NG+ exclusive (Fire)
Basically Riwo but only for 5 mana? It's a shame she isn't on NG otherwise, she would be a 10/10, maybe even 11/10 over Forzaslein, since you could deploy her + Noelia for the same cost as Forzaslein.
B. Eushully-Chain, Would be a 9/10 if she wan't NG+ exclusive
Another 5 cost unit that flies with 5 move, only drawback is that she focus on magic and has bad atk, so it's a bit harder to sweep maps compared to Eushully-Chan. Still 5 mana is great value for a good unit.
Spiri, Would be a between a 4/10 and a 6/10 if she wasn't NG+ exclusive (Wind)
The other most expensive unit to deploy at 15 mana. 5 Move and 3 Jump is nice I guess, but she doesn't fly, so it's a lot worse than the actual fliers to sweep maps. The best value is that she is free on the extra NG+ final missions, then she has completely lost one of her drawback for those maps only.
She is Wind, so at least she is useful sweeping Artefact enemies.
Karian: Would be around a 2/10, because she joins late even by NG+ standards (Fire)
Not only does she join late even by NG+ standard (earliest is Chapter 7, when the other NG+ units can be recruited in Chapter 2 or 4) she also has very poor movement of 3 and 1 jump and cost the same as Lutriche. Absolutely not worth the 12 mana.
So the ranking would be:
1 Forzaslein (10/10)
2 + 3 Riwo and Noelia (9/10)
4 Elballad (9/10)
5 and 6 Lavirie and Mistoria (8/10)
7 and 8. Tsumugi and Mezarbo (8/10)
9. Gu-Landio (7/10)
10, 11, 12 and 13 : Rishe, Kalema, Glarissa, Elgamisera, (All are BiS in specific maps) (6/10)
14 Nekol (5/10)
15 Patra (5/10)
16 Ardorkufel (5/10)
17 Forunisgein (4/10)
18 Koridora (4/10)
19 Lutriche (4/10)
20 Allargand (3/10)
21 and 22. Princheno and Agate (2/10)
23 Galanis Guardian (0/10)