Can you tell what are examples of FF class combinations and how it works? I only played FF Tactics Advance. As far as I can remember it the character was mostly defined by their current class, you only had active abilities from your current class and all others were passives.
Here in Fell Seal it felt like every character is too much. Almost every class already has a variety of active abilities and you can equip abilities of two classes. I gave every fighter Scoundrel secondary ability because it has attack from the back and movement buff, so you have something to do in almost every situation. Of course it may be a noob tactic only working on normal but it worked well. You can also give people, say, Templar class abilities which give healing AoE, ranged attack and melee AoE; Gambler who is a buffer, a debuffer, healer and damage dealer; Plague doctor who has healing, buffs, debuffs and pretty strong poison attack.