Debuff Formula in M17

thefabricant

Debuffs that reduce enemies defense post module 17 do not work in an intuitive manner. Here is an example:

Player:

• 1000 Armour Penetration.
  
• Jagged Dancing Blade pet (legendary).
  
• Ray of Enfeeblement (10% debuff).
  

Dummy:

• 750 Defense
  

With only the Jagged Dancing Blade active:
min((1-750/100000+1000/100000+8000/100000),1) * max(1-750/100000+8000/100000,1) = 107.25
With Jagged Dancing Blade+Ray of Enfeeblement:
min((1-750/100000+1000/100000+8000/100000),1) * max(1-750/100000+8000/100000,1)*1.1=1.17975

Resulting in a debuff formula as follows:
MIN(MAX(1-DR+RI+Σ[-DEF_DEBUFF],0.5),1)*MAX(1-DR+Σ[-DEF_DEBUFF],1)*(1+Σ[NORM_DEBUFF])
Where:

• DR = enemy damage reduction
  
• RI = player resistance ignored
  
• DEF_DEBUFF = debuffs that reduce an enemies defense
  
• NORM_DEBUFF = debuffs that multiply against an enemies defense
  

This system is not intuitive, at all. It causes any debuffs that reduce an enemies defense to either do nothing (in the case where you do not reduce an enemies defense with them to less than 0) or to debuff the enemy and increase the damage they take, by some arbitrary value depending on the difference between the debuff value and the enemies defense. There is no way to infer this behavior from these items tooltips and without an exact knowledge of what every single person in the group is using, there is no way to know if the debuff is doing anything at all. Furthermore, I do not think it is intended, as the whole purpose of the M16 rework is to prevent confusion like this.