I finished this on Saturday Nov. 10 but want to post my end game stats in case anyone is interested.
(Perhaps this will give folks an idea on the minimum required level to beat the game or help to avoid too much grinding):
Guardian: Astaroth (level 65)
My stats went all haywire when I switched to that specific guardian and I lost quite a bit of strength and HP but INT and MAG went up a lot! I waited until the bar was red and totally filled before dying at level 54...
Equip: (nothing special, most likely): Longinus, M134 Vulcan, Jagd helm, tetrajammer, parade glove, jagd leg, nerve bullet
Guardian: Dominion (level 52)
Equip: (nothing special, most likely): Shamshir, golden gun, panzer helm, panzer suit, panzer fist, panzer leg, nerve bullet
Seiryu: Level 48, 866 HP, useful for rakukaja especially
Chernobog: Level 46, 898 HP, one of his skills was useful
Byakko: Level 47, 765 HP, THANK YOU FOR ESTOMA
Cu Chulainn: Level 43, 586 HP, Tarukaja/Tetraaja were super useful. I think deathblow did great damage too.
Overall the last dungeon did not present much of a challenge when I was finally ready to tackle it (thanks estoma and trafuri, like really, thanks so much) and the last boss went down very easily for me. I do not remember what 2 minions of the 4 above did good damage but two of them did. I had one of those minions do a critical of 899 and another one did a critical of 699 but most of the time they did multi hits for around 240 to 260. Other than that damage was between 75 to 100 for the other four but most of the time, thankfully, were multi hit. I know the main character closed in on 100 after a bunch of the -kaja attack boosts....Not even sure if the -kaja and -raja spells stack, seems like they did to an extent but I had one and sometimes two demons who basically sat their casting those most turns because..whatever... but Yah, the damage was in those ranges or something like that, don't totally remember, I was just soooo ready to end this game long before I even got to the school (try the end of the sloth dungeon).
So yah, if you are like me and NEED to finish every single rpg you start, even if you dislike it and feel the same as I did about this game and are looking for a decent idea of the minimum needed to beat it, go for AT LEAST what I have give or take 2 or 3 levels...perhaps the game can be completed around level 48-50 even or maybe even a little lower, would not be shocked, in fact go for it at level 50, I am sure it is pretty easy with estoma by your side and it saves at least an hour of griding! Any way with my current set up I NEVER felt threatened though it was kind of a long battle because the last boss had so much HP and I had to use 1 or 2 Charka pots or whatever it is that heals MP but otherwise he never hurt me all that much.
Now that I beat this "gem" I feel I can freely state it is pretty darn bad, repetitive, a huge chore and it p*$$es me off how much the translating group responsible for this game was hounded considering how bad it is....I kept thinking as the end credits rolled "dear god they have no idea how bad this was in the end...All that fuss over...this? Come on."