I have always wanted to do a campaign that is something like the Monster Hunter games or Claymore, and would be very interested in this.
I feel there would need to be two 'health' bars, since getting hit by the kraken is usually game over.
One for actual health, and one that is used to dodge until you are tired, stamina or something.
I have no idea how this would work. Maybe determine the speed of the large creature, and therefor the difficulty of dodging it, then when the player rolls to dodge (with penaltys/bonuses based on how recently they attacked or moved?) consume stamina to close the gap on a failed roll.
I have little idea how damage would work honestly. I try to make combat in the games I have DM'd sound a bit like dwarf fortress adventure mode: "You hack them in the right foot with your axe, tearing through the flesh and digging into the bone, they scream in pain as they fall to the floor"
So I imagine if you were fighting say, a giant, and hacked it in the leg, each strike might reduce the health of the leg until you get to the juicy parts that matter, which then have an actual effect on the fight instead of just reducing the giant's health from 500 to 450.
Hit an artery? blood spilling out everywhere, roll reflex to avoid slipping and the giant takes damage/con penalty/cant focus due to blood loss/something.
Hit a bone hard enough? Giant hobbling on one foot, take down the other one and he will fall like a tree.
Not sure what hitting a nerve would do.
Anyone ever done this? Or know a system that does? Or anything like it really. Preferably with large creatures and not just localized damage.