Eh, I don't even bother to max things out. The hardest part for me was midgame of Gen 1, with that fucking cowardly general always running away. Then I got 2 heal spells and Resurrect and figured out linking characters/AI, and just stopped dying. In Gen2 I started to use auto-combat, only going for manual controls if I need to res someone. I also took a little time to get myself platinum weapons, because while I was winning it was taking just too long with random crap my party was wielding. Gen3 ramps up difficulty - fucking bees man, and large monsters are now casual mobs. Also compared to amazing Ladius'es "V" formation, which is very easy to use, Thoma's isn't that great. I married Sherufanir, obviously, because she is funny as hell, so Thoma became an AGI based guy who can wield swords and rapiers, which also isn't great.
But oddly he can also wield hammers, so I gave him a huge fucking warhammer and few bonuses from captured monsters for better STR, so he is effective. Not as Borgnine, of course, but noone is, because that tank has a bonus from upping his VIT from level 1, meaning now he has unparalleled HP of 7000+, more than any monsters.
Thoma's super attack, however, is a long ranged single target blast, which can be exploited greatly when fighting bosses.
I still carry floating eye Familiar. It's not that he is so great, but I can't find any other character who combines 3-5 different magics, dark magic (Capture!), high Luck, and Steal all in one package. My other monster is Salamander.
Ellis and seer chick also irreplaceable with their 100+ INT, even if their damaging skills are so fucking boring.
By the way RK47 are you going to use marionettes? Seen that guild? It's so creepy...