Relic Delta
Personally I can understand, that you wanna implement a system that improves the benefits of a player who has many high Relics. But the numbers I heard about (95 % dmg reduction for a low relic AND 95 % more dmg for a high relic) are ... insane. Instead, why you didn't change the linear scaling of the Relic Levels itself? For example from Relic 8 to Relic 9 there will be an even stronger boost. And from Relic 7 to 8, too. For example something like this for damage:
Relic 1 -> + 100
Relic 2 -> + 250
Relic 3 -> + 450
Relic 4 -> + 700
Relic 5 -> + 1000
Relic 6 -> + 1500
Relic 7 -> + 2200
Relic 8 -> + 3100
Relic 9 -> + 4200
(Additionally you can add, what you already do for some characters to most characters: add the relic tier to the abilitys.)
By adding a stronger boost, you would keep the integrity of your mod system alive. I like to get the maximum out of my roster with especially premium mods, but I will automatically loose against my GA enemies then. They have most of the time 2 - 3 million GM more than me (9 million).
I would highly recommend, that you should focus on buffs, that a player can choose.
For myself, this will decide if I would play the game in the future, or not.