It will only multiply the base stats before any other % modifiers are applied which include % modifiers from artifacts, DLC augments, affinity mods and SP. Did you test hybrid spec with all those things removed?
I've tested it over the past couple of weeks - it's giving 5% (as calcuated per illumin X above (base dom number *all modifiers applied at once after being added together (including the 5% hybrid).
Every % modifier works that way. It’s always Total Base Stat= (sum of all number stats)Sum of all % modifiers. Now, when you try to decypher how buffs and debuffs stack and calculate, that’s when it gets really confusing and complicated. I remember being disappointed last DLC when I realized the tank Adaptive (DLC) augments only multiplied the base defense from gear and excluded the automatic tank role defense buff. It follows suit but at the same time you never think of them as technically being separate pieces of the equation.