x% Reduction to enemy health?

Hey, this might sound silly, but what kind of damage skills or items that have this text apply?

Is it a universal “damage” that bypasses all armor and resistances?
Can you increase or resist this kind of damage anyhow?
Does it apply to enemy current health or total health?

It’s applied as it’s own damage type.
You can’t really increase it in any way.
Most bosses have massive innate resistance to it, rendering it worthless.
It’s based on total health.

It’s a damage type that for the most part, only works vs players, who for the most part either have 0% or even -25% resistance to it, with only a grand total of 3 items giving resistance to it. Only 2 enemies in the game use it consistently, on an easy to dodge projectile skill. Every other instance of it is on weapons for a very small value.

http://www.grimdawn.com/guide/gameplay/combat.php#q07

Unless something changed and rendered the guide obsolete, it is current health.