How that all changes going into Battle for Azeroth remains to be seen.
Traditionally, the first kill video is released by the first guild to down the boss, nabbing them the viewer figures, ad revenue, and props. This wasn’t the first time the entire fight was publicly available, as Chinese guild Alpha, who were the world fourth kill yesterday, streamed their progression and eventual victory. They then use the resurrection tree – itself meant to keep players alive through various bits of raid-wide damage by providing extra lives – while a Monk tank uses their unique abilities to survive Argus’ massive single-target damage for a few seconds. This was apparently to dodge a mechanic that otherwise puts a damage over time effect on the entire raid for more than healers could easily keep up with.
You’ll notice at one point they all die, outside of the phase transition in the fight. My two favourite moments are everyone telling somebody to shut up when they say this is going to be the kill – well at least they were right – and the total panic when the lack of a kill notification implies there’s going to be another stage of the fight at the end.