Re: Desolator vs Buriza
"Enemy Armor" is the current armor of the enemy, before Stygian reduction.
If you want to add more armor reducing abilities, just consider that the current enemy armor is already reduced by all of these abilities, except Stygian, since you're only comparing Stygian and Buriza.
For instance, if you want the number for someone with 20 armor under the effect of Amplify Damage level 3, just look at the number for 5 armor.
(ie the entire graph is shifted)
(Also, armor cannot go below -20)