This is something that I have been giving a lot of thought on for a number of years as my rpg group in general does not like the loads of hit points school of playing. In particular we nearly always use mooks with low levels of hit pots for most npc. In general only one or two htis are needed to knock them out of the fight.
My current thought on DnD hit points is that the additional hit points above constitution are basically a buffer, allowing the pc to absorb damage, certainly because of experience and skill in line with the dnd next rules. This means that those hits are not actual physical just numerous small nicks and scratches have started to take their toll, just like Conan in the books, or equivilent to using a Fate Point each time you are hit.
The key would appear to be what happens when a ch…