so above 43 is just a visual bug after 20 hard points?
Yup
3 + [2 x hard points]%
From 5 to 43%
It works against all dmg types and is applied after all other dmg reductions you have (res, dr, sorb, mdr, pdr, etc).
So even if you are down to -100res
you still only take 114% dmg (instead of 200%)
And if you have 75% res, instead of taking 25% dmg you take 14.25%
It’s op.