There is no condition to only stop when a pool of blood is created, though. Start a new game on hard with a lone wolf leech maxing constitution, and you can heal to less than full health at level 1 with no other HP bonuses. The reason a pool of blood is created after healing stops is because there is more blood produced than the character can currently heal with their hit point value, not because that is the condition for it stopping.
So later on it's more balanced? Might wanna make Leech require being a higher level before it unlocks then.
