Why is this rune in this game?

Once I said this title you probably already know what I'm talking about. I don't understand why conqueror is in this game to be honest it is just insanely broken, you see someone doing 2k true damage with the mastery in 20 minutes while people with electrocute only did about 800 it really doesn't make sense. Every game I play I just check the damage conqueror does and its off the charts compared to every mastery it really doesn't make sense why it could do this, if they really wanted to add a new rune they should've added something more of a utility kind of how guardian, Klepto, and glacial are. This rune needs to be nerfed because champs who already have true damage are taking this so its almost like you can't even build armor against them and its so annoying because before you can even build enough health they are just penetrating straight through you and you are defenseless. I also hate those who say this mastery isn't broken like do you not see the damage output it is giving and how easy it is to proc.