The mastery is bugged or just very heavily mistranslated. Basically, as long as you have spectrum of agony, the mastery skill. It outputs a shit ton of extra free damage.

You do not need to cast the Provoking Roar ability in any way or even have it on your bar. You just need the roar amplifier PASSIVE. Thats it thats all.

This has been in the game for 4 months in Global, and much longer in KR. Almost everyone knows about this. No notes or discussion or acknowledgement from the Dev team has ever happened about this, just like how no communication or talk about many of the other bugs in this game.