Off that will happen i am at 1k i only melee, it hits 3200 on prayer without zerk, while zerking it was around 4900 as i recall, literally the kill was fun 😂, but we did it 1k melee 😎👍🏻
Different armors have different values for damage reduction that is different from armor rating, you can see the total value of worn equipment from your "worn equipment" and at the bottom there's red & blue lined icon that says "view your combat stats based on your equipped items" and at the bottom you can see "damage reduction (PvE) and damage reduction (PvP)" On top of that you've the possible armor based damage reductions or off-sets such as cryptbloom and trimmed masterwork armor.
9months late to the party...but...he is using berserker aura...it makes you deal but also take more damage. then he did the ultimate ability berserk who does the same but to a bigger deggree and its a 4000% so he is in teory taking 160% base damage but he is also in paper armour so like no damage reduction or absorbson at all. you could do this at 4k telos to if you have the enrage unlocked :P or zamorak :P
