tested with rock golem in hole... uncharmed hitting for 180s 20% debuff should decrease the hits to to around 150/160 currently hitting 110/120 So instead of the decrease to 20% like stated its currently the 40% for PoP and beyond
Math is hard. Chances are the scaling affects the NPCs base value (the same one that defensive impacts) which would lower it more than 20% Of their raw damage. Also even if that's not the case 180*0.8=144
Are you comparing the mob hitting you to the charmed mob hitting another mob? I'm not sure thats apples to apples my dude. For starters I'm guessing the NPC has more mitigation then you do. If you want to get apples to apples your going to have to find a parse from before and test with the same level/type of npc charmed or duel someone and have the charmed pet hit them and then break charm and let it hit them some more and compare the numbers.