I thought about it a lot last night, and I thought of some simple formulas, but I'm still not too sure. At the beginning while your strength is relatively low and your weapon isn't the strongest, you would only be dealing around 1-3 damage at a time. I don't think I'd ever want them to hit 0.
Actually, in Kingdom Hearts damage is pretty static. While you do more damage at higher strength levels, you always do the same amount with a random critical hit every once in a while. It usually gets stronger as your combo drags out. E.g. The first hit is 3, then 5, and then 7, and when you use the finishing move it will do the most damage, like around 14 in this example.
The battles wouldn't really consist of healing much. Normal enemies are not meant to be devastatingly hard, but more of something to train on. For example the most basic enemies AI will consist of:
Hide
Sneak to the player
Surface
Attempt to attack
Repeat.
Depending on the difficulty level it would also take a varying amount of hits before you die. That particular enemy (the weakest one in the game) would take around 10-13 hits to kill you on beginner mode, 5-7 on normal mode, and 3-5 on proud mode. Which of course becomes easier to survive as you gain HP and enemies stay the same. It also becomes extremely easy to stay alive once certain abilities are unlocked like second chance and once more. Not counting the fact the you will have Cure, Cura, or Curaga through most of the game.
Idk, overall this is probably the funnest part for me. I like spriting and all, but it is becoming a chore and I just want to finish so I can release my first world's demo which only involves 2 or 3 fights.