Cada criatura recebe o dano completamente
A linguagem é direta nisso (minha ênfase)
each creature within 10 feet of the hulk takes that damage instead
Esta é uma linguagem idêntica a Bola de fogo (ênfase minha):
Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one.
Em ambos os casos, cada criatura é obrigada a receber o dano causado pelo feitiço. Não há pool de dano compartilhado.
Note que o Sleep tem um mecanismo de pool:
Starting with the creature that has the lowest current hit points, each creature affected by this spell falls unconscious until the spell ends, the sleeper takes damage, or someone uses an action to shake or slap the sleeper awake. Subtract each creature's hit points from the total before moving on to the creature with the next lowest hit points. A creature's hit points must be equal to or less than the remaining total for that creature to be affected.