Considering this has now been shared over on 最高DPS两千万！9人15秒击杀M尼珊德拉 _ 多玩魔兽世界专区 I don't mind posting it here.
Back in 7.1, up until 7.3 you were able to obtain an item in game that effectively tripled your damage, but it was stackable. This meant that if 5 players used the item you could increase your damage by 300% x 5. Below are the results:
Enjoy, purely now educational as it's fixed.
Special thanks to everyone in this particular video, but also to RAOV for the memes
Thanks,