So, gameplay notes. My final party was Clarissa/Labby/Felius/Levin/generic Enigmancer with Sacred Slayer stuff/generic Nightstalker with Secutor equips and ATK +25%. Labby was an Enigmancer, and the other plot PCs were in their unique classes to take advantage of the extra skill slots.
Clarissa: I'm pretty sure I used her for every plot battle in the game. Usually I had her sitting in whatever class would give her the highest RFX in order to exploit Encourage (mid-game, this was Excavator; she went to Nightstalker and stayed there until maxed once that class opened up). Generally served as utility player: she had Mystic and Sacred Slayer OC, so she could boost someone in an emergency whenever needed. Find it funny that Dhyer turned her into a damage queen, because I almost never used her for this (sure, Sacrifice is badass, and I used it when feasible, but mostly other people handled offense on my team).
Felius: Sat out most of the midgame because magic was consistently better for offense than physicals. Left him sitting in Secutor without much in the way of plans for him. This actually turned out pretty well once I got the last batch of classes and could easily give him Six Shooter to go with that high ATK. Basically didn't leave the party after that. One-dimensional, but anything without noteworthy evade got shredded.
Labyrinthia: Good unique skills, good magic stats. Made her into the team cannon; any time Turn Shift spam happened, it was directed at her. Along with Clarissa and Levin, almost always in the party.
Levin: High speed plus Cancel Strike makes him ideal for cheesing out boss fights, and Blast is great just for being ranged damage you can use after moving. I taught him a variety of magic skills and then switched him back to Martial Mage to take advantage of its superior mobility. I never even got around to teaching him MAG +25% or Widespread and he still kicked ass. Had everything I needed for any serious boss fight. Probably MVP.
Tony: Is doglike. So, he sucks in battle. Idly, I have to wonder a little about Tony in the plot. The penultimate boss says something about a "A mere dog resisting my power." I have a vague recollection of some random townsperson, much earlier in the game, talking about the Guardians and saying only one of them was actually still manifest in the corporeal world. Tony = Luceid?
Ragnar: Had accuracy problems the whole game, it seemed. I wanted to make use of him just for the sake of his other base stats being decent, but somehow he just never worked. Raving Revenge as a counter is pretty cool in theory, but boomerangs seemed to suck compared to other weapons and this just defeated the point. He didn't really get used after Act 2.
[Tide]: Shame about that speed. I never could settle on what to do with her and she mostly just took up space in the reserves. Gave her High Cavalier stuff and some other assorted physical abilities, but nothing seemed to synergize that well with her unique skills. Exhaust Strike did come into play for some of the more durable bosses, though.
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Secutor: Not that great by itself, but the attack boost and equips let you do horrible things to enemies in conjunction with lategame skills (read: Six Shooter). It was only very early and very late in the game that I did anything with Secutors. Rating: C+
Elementalist: Good early on, but I eventually took the skills and went elsewhere. Crappy non-MAG stats, and a lot of the second half's plot bosses have resists that make Elementalist offense insignificant. Their weapons are the best for any spellcasting PC, though, and MAG +25% should be part of any mage build. Rating: A-
Fantastica: Gives you Slow Down, which is eventually eclipsed by Debilitator but still useful for a very long time. Invoke and Rush are useful too (moreso the latter for me, since mages were always dealing the bulk of my damage). The class itself kind of sucks, but you can get a lot of mileage out of the skills if you transfer them to another class. Rating: B-
Gadgeteer: It gives you Mystic. That alone is worthwhile. I got some use out of Decelerate too, but yeah, it is mostly about the OC here. Rating: C+
Sentinel: Crap. I only used this class when forced to do so by the game. DEF +25% is accessible fairly early, which I guess is nice to transfer to other fighter classes, but that's about the only thing I can compliment Sentinel for. Rating: D-
Sacred Slayer: Augh, that speed. Still a pretty good class, though. Why? TURN SHIFT. It breaks the game into little pieces. What else do you need to know? Even if you choose not to cheese XF out with that spell (and I mostly did opt not to for maps that didn't actively engage in douchebaggery), it still gives you some great defensive stats, healing, and Widespread. Rating: A
Excavator: Mostly pointless. Clarissa stayed an Excavator for much of the midgame because I needed to make use of its high speed, but I don't think I ever used its abilities, passive or active, again outside of that one plot battle where it's required. Well, I did experiment a little with Detect shortly after that plot battle, but I almost never found anything. Much like the Geomancer's leypoints, the game didn't seem interested in making use of the hidden item mechanic after it was introduced. Rating: D
Geomancer: Worse than Sentinel. Even Shut Out is barely worth the time. ...Okay, I guess Shut Out is objectively better than anything Sentinel can give you, but I hate Geomancer just for being bad at everything. Rating: F
Berserker: Well, the mobility is great, and my fighters spent a fair amount of time in Berserker just for that. Any map with a time limit practically demands a Berserker or two. They're shafted on maps that don't allow for easy, straight-line movement, though, and the attack skills are so specifically situational that I almost never used them. Not for lack of trying, as their charge deals pretty good damage at max range, but the zero vertical tolerance is just a killer. Decent class overall, wish I could've got more use out of Valiant (it was late in the game before I had anyone max Berserker). Rating: B-
Enigmancer: Awesome. This is what most of my spellcasters were by endgame (only exception was Levin). More balanced stats than Elementalist, Devastate is excellent damage, and the ability to ignore friendly fire works great in conjunction with Sacred Slayer's Widespread. Rating: A+
Grappler: Pretty good. I had a lot of people spend time in this class just to get Accelerator, but Red Zone has its uses and the attack skills are pretty good too. A lot of my PCs had Grappler OC on even at endgame just for Heavy Throw. So, your mages are too slow to move into Devastate range? No problem, just have a fighter hurl the enemy closer to your front line and do damage at the same time. Chucking people off cliffs is also great for any enemy with high weight. Rating: B+
Strider: Honestly, I never found a real use for this class. Plenty of my fighters could've used AIM +25%, but it would've required spending a lot of time to max out a class that otherwise didn't seem to have any purpose (and most PCs only got enough CSP to max out two classes, three at most, so this wasn't about to be one of them). The sheer irritation of enemy Striders spamming Swift Shock makes me suspect I should've used them more, but eh. Rating: D
Nightstalker: Speed. Demon. I initially found Nightstalker very useful for that reason alone. Then I gave the Nightstalker attacks to PCs that actually had enough strength to make good use of them, and the enemies cried. Granted, Six Shooter in particular is badly nerfed by significant evade (the lategame bosses all seem to have a respectable amount of it), but for a time it makes your physical offense just terrifying. Also, I can't count how many times Illusion saved someone in this otherwise frail class from getting splattered. Rating: A-
High Cavalier: Seemed pretty balanced, but I didn't get much use out of it. Several of the final classes suffered this kind of neglect due to me having mostly decided what various PCs were going to be doing by the time this set showed up (level 7 of any class requires so much CSP that you know someone will have to stay in it for a long time). Rating: B, giving it the benefit of the doubt.
Emulator: Barely used it. Spellcasting with good range even after moving is objectively great, but the stats looked like ass. Exploit Weakness would've been useful much earllier in the game, but the important lategame enemies don't have weaknesses. Basically, a lot of neat abilities that seemed like too much trouble to unlock given how late you get the class. Rating: C
Extremist: I barely used the actual class, but I think like half my party had Extremist skills. Debilitator is indispensable for any boss fight, and it takes you all of 8 CSP to unlock. It could be attached to the shittiest class in the game and it would still be worth getting. Rating: A- because Debilitator is just that badass.