Your statement makes no sense, and even what you meant, is extremely ironic.
Concentration damage is additive with all other sources that increase damage by a percentage, for pretty much all the compatible skills in the game.
Magic dmg % is clearly an exception, with blessed hammer at least.
Nice try.
it makes tons of sense
concentration shouldn't work with blessed hammer, but it does due to a bug that was never fixed. Given how it multiplies the magic damage of blessed hammer in a way it shouldnt, the equation works like this:
(B hammer damage x magic damage % ) x Conc %
so yes.. if you know how conc works, you would not expect magic damage % to be additive to conc %, as conc % isn't magic damage % like how lightning mastery is lightning damage % and thus a lightning facet is just additive to the already existing lightning damage % you have.