World First Heroic Jailer Kill by Alpha in Sepulcher of the First Ones

wowhead.com:

The Chinese guild Alpha (阿尔法) is the first guild in the world to defeat Heroic Jailer in Sepulcher of the First Ones! Screenshot courtesy of Raider.io Although we do not yet have a clip or the usual breakdown provided by Raider.io, it appears that the 22 person raid included:Tanks: A Brewmaster Monk and Blood Death KnightHealers: 2 Restoration Shaman, 2 Holy Paladins, and 1 Restoration Druid, Melee DPS: 3 Warriors, 2 Rogues, 1 Death Knight, 1 Demon Hunter, and 1 Enhancement ShamanRanged DPS: 2 Hunters, 1 Warlock, 1 Boomkin, 2 Mages, and what appears to be either either a third Mage or perhaps an Elemental Shaman. Many guilds opted to skip the Jailer, due to the perceived weakness of his loot table — although he drops higher item level loot than the raids first eight bosses and many of the items are quite strong in their own right, they are nowhere near as valuable as completing tier set bonuses.

Therefore, the majority of guilds have opted to skip the Jailer and instead prioritize additional Heroic, Normal, and even LFR groups, or heading straight into Mythic in order to get to those tier bosses instead.