FREJO'S PROFILE

Kestral was setup as support/jack-of-all trades, his subclass was Beast Tamer and his main class changed depending on my needs, he was usually a Captain but would also sometimes be a Shaman a Healer or a Dark Knight. His role was to heal with Healing Wind and White Wind, use healing and buffing items as needed and apply whatever status effects and debuffs the boss is vulnerable to; on free turns he would either use Double Time to give an extra turn to Mari/Dante or use one of the 2-hit elemental spells since they do pretty good damage. On mobs he would just spam Tsunami/Fire Breath/Tremor/Magnetic Field.

Mari was pure magic damage wit Arcanist as main class and Dark Knight as subclass for Bloodoath and Malefficient Harm (and gravity spells for mobs). She was my main source of damage, basically using Bloodoath->the 2 non-elemental spells from the arcanist->Malefficient Harm and then repeating this pattern for consistent damage, if needed she can also buff my party's magic though she herself doesn't need it since she has the accesory which grants the auto magic buff. She also has the Bunny Slippers for auto-haste along with the gauntlet for 0 MP cost.

Dante was my tank/physical damage with Guardian and Warrior as his classes (if I needed him to tank then Guardian as main and Warrior as sub and viceversa when I wanted more damage). With Alarming Presence he draws most of the enemies attacks to him. He would usually start with the party-wide defensive buff and then follow up with the Warrior's break skills to debuff, if the enemy is immune to debuffs or is already fully debuffed he buffs my party's attack and proceeds to spam Triple Thrust/Flurry/Double Slash/Cleave. He has the shield which nulls stun, the armor which grants auto defense buff (would have helped a lot against Caelia if I had it then), and Lucian's Hat+the accessory which grants 25% resistance to everything for 50% resistance (tbh I'm not sure if they stack).

P.S. I feel that the robe you get for defeating one of the 4 pilar bosses in the moon tower (the one that grants full status immunity) is not very good since by that point you probably already are immune to all statuses thanks to passive skills, I believe it also doesn't protect you against stun, debuff immunity may be better since Melfice spams Debilitate (though things like elemental resistances, extra HP and so on would also be useful).

Glad to be helpful! While I'm at it I also wanted to comment on the story and classes ( warning! wall of text incoming)

Story.
I found it pretty enjoyable, part of it is because with the introduction on the page I expected an Excuse Plot and was gladly surprised when it wasn't like that; the little interactions on every Danger Hex help build the main characters and their relationship at a pretty decent pace; the story starts light in the beginning and builds up the mysteries to keep you expectant of what's to come and it all kinda ties well together in the end.
My main complaint is the fact that Kestral's sister gets pretty much no backstory at all, how and why did she die? why is Kestral so intent on resurrecting her? and so on.
I also felt that the timeline was a bit messed up. Kestral rescued Mari and all 3 main characters lived with Kestral's father who forged their swords, then the 3 of them went on a journey before stumbling on Terrarium rumours, all of this should have taken quite a while. Meanwhile Dante's companion already found the ruins which probably means Mari's father was already in the final stages of his plan so he just kinda derped around while the main characters travelled around the world, he also apparently never tried to hunt them down even though Kestral lived in a nearby village ( he also could have brainwashed Kestral when making him his assistant, but that's typical villain stupidity so it's okay).
I personally feel that Mari's portrait doesnt fit her at all since she has the typical female villain getup but Mari is an innocent child type of character.
My favorite character was Dante, he initially came off as the typical brute warrior but ended up mostly as comedic relief and was overall pretty likeable. Mari felt a bit stereotypical for the most part and Kestral was a bit bland until the last parts of the main story.

Classes.
Warrior and Arcanist were the best classes for physical and magical damage respectively, Warrior's debuffs are incredibly useful and the Arcanist's AoE helps clean up fights fast.
Beast Tamer is a great class because it's extremelly versatile, it can heal, do decent magic damage (a bit lacking in good physical moves imo) and apply useful debuffs and status effects, I think it would be nice to give at least a few learnable skills to the class since otherwise there's really no point to taking it as a main class ( I think the extra experience one is fitting, the Drive Master is a very melee oriented class so magical builded characters have a hard time learning it, the beast tamer has both good attack and magic so anyone can take it up without ending as deadweight).
Shaman got kinda outclassed by Beast Tamer halfway through the game since it can apply all of it's debuffs except for 3 of the elemental curses ( it also gets Tremor which is better than Avalanche) while the buff removal can be done by a Warrior.
Captain was useful as an early healer but gets kinda useless once you get auto HP and MP regen, Double Action is still pretty good on a support character though. His offensive skills are OK.
Guardian was mainly useful for Alarming Presence and the defense buff, as well as the stun move; I didn't really learn any of it's other active skills since they seemed really situational/unreliable and I didn't particuarly need the pure damage skills since I already had the Warrior/Drive Master for that.
Dark Knight is great as a subclass, an Arcanist/Warrior with both offensive buffs and Bloodoath can deal insane amounts of damage and it gives you several powerful nukes to use when your main class' skills are on cooldown (the highest damage I ever dealt was 45000 with Malefficient Harm on Arcanist Mari), it's Demi attacks are very useful on mob fights and don't require any offensive stats to do their job.
Healer has extremely useful passives and useful actives, but it kinda gets redundant once you can just spam healthy feasts (with that 50% extra healing), it's usually enough to heal your party to almost full ( and you can just use soul tonics for full revive), still useful in hard fights where that isn't enough I guess. There's also the Beast Tamer's White Wind though it does have a 1-turn cooldown.
Drive Master is great for early game damage when you still haven't got a lot of ways to spend your DRIVE and has some situationally useful passives and elemental actives, for boss fights I would still pick Warrior over it cause debuffs. The full heal+revival can be useful on though fights.
Hunter is imo the worst class since it's slayer skills are all pretty situational, Nature's Wrath is not that good on a class with such low Int, even if it's only to slow the enemy down and apply fire weakness it would still make way more sense for the Shaman to have it. The attack that hits 6 times is good against single targets but terrible against groups and it's ultimate feels a little bit on the weaker side. While I understand not giving unique steals to prevent missing out on them, this is usually the main atractive of Thief-like classes in most rpg's: being able to obtain powerful/rare weapons and equipment from bosses and mobs that cannot be obtained otherwise. I didnt particularly feel like I needed to obtain every single crafted equipment so there was no reason to try to obtain more materials through stealing (except in the postgame dungeon). Accuracy buffs are also kinda not that useful since you don't miss that often.

P.S Regarding the Summons, all of them deal very good damage, which means that the ones that can do things other than only pure damage are the most useful, I usually used Babush for his buff and stun or Angel/ Fairy if I only needed minor healing so that I could focus on offense, Kyrie was the most general purpose out of the summons, she can do good damage, heal Kestral, inflict Curse, Poison and magic debuffs and buff your team's magic.

Ok, I fought Melfice again and learned Sacrifice from him, the first time I simply didn't try since I thought he would be immune to taming.

Regarding the difficulty; I played through the whole game on Extreme and thought that it was okay, I had the most trouble during the first dungeon (didn't have a lot to work with) and the second and third bosses (they did too much damage so I ended up having to play defensively and just let the shaman's poison do the work for me), didn't have much trouble after that.
I did grind twice, once halfway through the game (I wanted some useful skills like half MP costs, auto HP and MP regen, 50% more healing and extra experience on everyone), and again in the postgame (since I wanted most of the passive boost skills and the status immunities).
The bosses from the moon tower were a bit too easy considering they are supposed to be fought after Caelia (whom I consider the hardest boss from the game), I think it's okay for the 4 pillar bosses since they come after two regular battles but Melfice could have been harder (maybe have him get stronger for each seed killed?)