Here's a post about how great I am, who doesn't love those?
Persona 4 on hard mode required me to grind twice, and twice only: Yukari's Shadow and Kanji's Shadow. I am sure you can win these battles on hard without too much grinding - for example, make Personas that give fire and physical resists, respectively. After that, on hard, there was no grinding required ever again - something that I really do appreciate. It reminds me of Final Fantasy 4 where, again, the only "grinding" you need is at the very, very start for maybe ten minutes, and when you turn a paladin for another ten, and then, if you can not defeat him, again for the last boss.
I think people who grind a lot in jRPG's are just doing it wrong - in general. I wouldn't call "don't flee from encounters while exploring" grinding either.
Persona 3 on hard, though.... I bought that game eight months ago and I haven't played more than 2 in-game months yet or so, simply because hard mode in that game is just suffocatingly harsh. I had to grind for every single mid-boss so far. The bosses themselves were easy, but getting there was not. I'll definitively say I find 3 a lot, a lot more harsh than 4.
Edit: Mitsuo didn't ever give me trouble. Are you using all the buffs and debuffs you can? I don't remember if there is, but if there is a haste spell, do use that too. And of course focus/mind charge, and some timing. I do think it's that kind of battle where you are supposed to lose on your first try.