How does Resurgence work?

Question

The Assassin/Zero's Resurgence skill restores health with melee kills depending on his own health. How do the health benefits scale with your health? What constitutes "low health" for the purposes of getting the maximum 4% life return on a melee kill?

Answer 1

You are, effectively, healed for a percentage of your missing health. Level 5 resurgence restores 20% of your missing health. So say you are damaged to 50% of your maximum health; killing an enemy with a melee attack would then heal you for 10%, putting your health at 60%. Alternatively, if you activate resurgence while you are at, say 10% of your health you will be cured back to 38%.

MBreadley's formula is correct.

Answer 2

The health gained ranges from 0% to the maximum amount in an approximately linear scale, For instance, say five ranks are invested in the skill, giving a maximum of 20% health per kill. If Zer0 has an extremely low amount of health, the skill will heal him for the full 20%, but if he has 50% health, it will heal him for half that, or 10%. If he has 99% health, the skill will only heal for 1% of the maximum, or 0.2%. In effect, Zer0 is healed for 20% of the health he has missing from his maximum.

(Taken from here)

And for low health - after checking some web sites I assume is everything below ~25-30% of your total HP, or to make it simpler - when your health bar start blinking :D (well that's what I noticed myself). I am sure if you make killing blow at that point you should get maximum % of restoration.