Tier 10-Heroic LK 1st Kill March 26th, Video March 31st, World 2nd kill April 11th, World 5th April 17th
Tier 11-Heroic Sinestra 1st kill Jan 20th, Video Jan 22nd, 2nd kill Jan 22nd, 5th kill Jan 27th (this one is a bit odd to pin down on wowprogress because of the different end bosses, I just went with Sinestra)
Tier 12-Heroic Rag 1st Kill Jul 19th, Video Jul 27th, 2nd Kill Jul 26th, 5th kill Aug 1st
Tier 13-Heroic Madness 1st Kill Dec 20th, Video Dec 25th, 2nd kill Dec 24th, 5th Kill Dec 27th
Tier 14-Heroic Sha of Fear 1st Kill Nov 25th, Video Nov 27th, 2nd kill Nov 27th, 5th Kill Nov 27th
Tier 15-Heroic Ra-den 1st Kill Apr 11th, Video Apr 22nd, 2nd kill April 19th, 5th kill April 23rd
Just for poops and giggles, Heroic Lei Shen 1st March 26th, video Apr 4th, 2nd kill Apr 1, 5th kill Apr 11th
Tier 16-Heroic Garrosh 1st Kill Oct 1st, Video Oct 6th, 2nd Kill Oct 3rd, 5th Kill Oct 10th
Tier 17-Mythic Imperator Dec 13th, Video Dec 18th, 2nd Kill Dec 14th, 5th Kill Dec 18th
Tier 17 cont-Mythic Blackhand 1st Kill Feb 20th, Video March 6th, 2nd Kill Feb 25th, 5th Kill March 6th
Tier 18-Mythic Archimonde 1st Kill Jul 16th, Video Jul 28th, 2nd Kill Jul 18th, 5th Kill Jul 30th
Tier 19-Mythic Xavius Sep 29th, Video Oct 1st, 2nd Sep 29th (Looking at WoW progress, at least 8 guilds had Xavius before video released)
Tier 19-Mythic Helya Nov 19th, Video Nov 21st, 2nd Kill Nov 19th, 5th Kill Nov 27th
It's only happened 3 times in 7 years of raiding that a guild has waited for a 5th kill. 2 of which are considered the same tier of content. I didn't even include other starting expansion bosses within the same tier like Nefarian, Al'Akir, Will of the Emperor or Grand Empress. I would almost guarantee that those bosses didn't wait either.
Saying it's been a "known rule for a few expansions now" is laughable when it is clearly not the case. Slootbag may have said it, but no one is following it. Heck even they aren't even following it this expansion so far. Mythic Gul'dan may be the first case of that this expansion. But everyone saying this rule of 5 has existed for a long time...no it hasn't. It's a new thing, if you can call it that, because again, they aren't even following it. And 3, possibly 4 with Gul'dan, bosses out of 13 (probably more like 17 counting the bosses I didn't list) makes them more exceptions to any kind of rule than there actually being one.
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All the time frames for world first kills and videos are from 25 man kills or mythic difficulties. No one counts a 10 man kill as world first. Oh and wowprogress doesn't even list that asian guild in the top 5 for either 10 or 25 man Heroic Garrosh.
https://www.wowprogress.com/rating.tier16
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If you want actual links to every single thing, I can do that just to prove how right I am.
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I am not complaining about the video not being released. I simply asked where it was. The answer I got about this rule of 5, I had never heard of till this thread. And now I am providing evidence in the form of dates of world first kills and their videos and then when the 5th guild cleared it. And there are only 3 instances of the world first video being released after a 5th kill going all the way back to heroic Lich King.