I honestly don't see what more I could have done with the combat system though? I had H'aanit + Apothecary, Ophilia + Scholar, Cyrus + Dancer, Therion + Warrior. If I knew of a passive that would benefit someone, I'd get them it. I didn't really see any value in swapping jobs much because at the end of the day, I'd still end up with a similar mix because most fights are the same in the sense that you need buff + debuffs, multi-hit attacks for breaks, heavy hitters for massive damage, and healing.
I literally do as you suggest for battles. I would delay Breaks until I had properly set up buffs and debuffs, and then I'd usually use Ophilia's special skill to give H'aanit the x2 skill ability, hit for double 9k+, also hit for 9k+ with Therion, and generally use Cyrus to help manage BP or individual healing if necessary before the next phase. Yet at level 45 I wouldn't survive long enough to do it enough times before the final bosses would randomly OHKO me, much less 10 levels lower than that like you're suggesting. Levels very much had a big impact on my ability to get through fights in my experience.
The game encourages me to not explore because I get destroyed everywhere off the main path, so I'm guided away from those areas for now, therefore I'm underleveled for main missions and also get destroyed there, therefore I'm left with no option but to grind really... Utilizing the battle system doesn't even matter when you just die so fast anyway. I've heard quite a lot of people say the game is easy when you know to steal (and reset 50+ times I might add) or find x specific thing, but how is anyone supposed to know that when they're playing blind? If they don't know, are they then playing wrong? It just feels like the game isn't giving you much freedom to actually get through it. I'm just one of many who apparently played it wrong and didn't get the message the game was trying to tell me (and in fact was guided to think the opposite).