With 5 Razorfoot Griffons in the team, I do the same damage (all of my damage comes from Acrobatics) with Shackler’s Mastery, that should add 20% damage for each of the Griffons, or Grim Aura, that adds 20% of Speed as damage.
Also, at high enemy levels, some attacks randomly do 0 damage (1 with Rage) then start doing the normal 40 million.
Edit: Wait, could it be that Deafening Roar doesn’t stack? I tested it and seemed to stack, but there’s so much variance in the damage that who knows.
Edit 2: Adding Grim Aura or a sixth Deafening Roar on top of the Mastery doesn’t increase the damage at all. It seems 41M is the maximum I can do for some reason.