An example of what I mean, about there being little middle ground.
Was in Ysgramor's Tomb, and you fight a bunch of mobs all called "Companion Ghost". In one room, the first two die in one hit each. They do almost no damage to me if they hit.
The third mob in the room, with the same name as the other two, one-hit kills *me* from almost full health.
There is no middle ground! On a harder difficulty two of those mobs would have been challenging and one impossible.
On an easier difficulty one "normal" mob and two trivial mobs.
But on the middle/default difficulty, two of those mobs are trivial and one insta-gibs me as I run up to it. Does that not strike anyone as strange?
Anyway, I've found out a bit about why NPCs have are able to kill you from almost full health. The game mechanics are truly awful in this regard.
In order to determine if an NPC can one-hit kill you, the game calculates how hard the NPC would hit /if you had no armour on/. If the hit would kill you with no armour on, the NPC does a "killing blow" animation.
In other words, killing blows completely ignore your armour. The more you invest in armour and defense, the more this game mechanic laughs in your face.
With a lot of armour, an ordinary hit might barely scratch you, but you might still get insta-gibbed by a "finishing blow" at 80%+ health.
You almost couldn't invent worse mechanics if you tried.