Kinda ridiculous; I've rarely found myself struggling, and I once fought a Lv. 30-something Veluza with my low-20s Maschiff and won (though narrowly - it had cut its HP in half first with Fillet Away, then failed to KO me next turn, allowing me to knock it out).
Beat a Titan? Fully healed afterwards. Those picnic NPCs you occasionally find - free full heal, though optional.