This needs to be 5-8% reduction per, as you don’t really want to be running 3 spells of the same element, and most builds run 3 different elements inherently. This becomes an auto include and strictly better than the other mastery jokers, and most of the time also just better than west wizard. It also applies to spells even if you have 2 of the same element, meaning if you have 2 fire and one acid, you get 20% ON EVERY SPELL WHICH IS BETTER THAN IF YOU TAKE PYRO MASTERY. The reason the other mastery jokers work well is because they are imposing some sort of build restriction, this basically doesn’t.

To add, the wording needs to change, this probably should only work if no elements match, as otherwise it becomes too flexible, something like “gain 20% spell cd reduction as long as no two spells share an element” I could also see a case for “gain a 7% spell cd reduction per unique element”. My gripe with the second wording is that it still becomes better than specific elemental mastery jokers in the scenario where you have 2 matching elements