Some hotfixes were pushed to live servers earlier today which nerfs various Mythic Sepulcher encounters including Mythic Vigilant Guardian.
Vigilant Guardian Vigilant Guardian health reduced by 10% The Vigilant Guardian creates a Spike of Creation at the target location. A player coming into contact with the Spike of Creation will cause it to explode, 29981499 Cosmic damage every 1 sec for until canceled to all players.]29981499 Cosmic damage to all players.] Effect #1 Effect #1 Apply Aura: Periodic Damage Modifies Damage/Healing Done Value: 3.999932 Difficulty: Mythic Artificer Xy'mox Progenitor relics radiate energy every 2 sec, inflicting 7494 Cosmic damage to all players and increasing damage taken from Ancient Exhaust by 20%12%.Effect #1 Effect #2 Apply Aura: Mod Mechanic Damage % Modifies Resource Generation Value: 2012 Prototype Pantheon Inflicts 224829112414 Physical damage to players within 4 yds of the Night Hunter's target. Damage is reduced for each player in the path of the Night Hunter.
Effect #1 Effect #1 School Damage Value: 300150 The Prototype of Absolution creates images of himself that mark random players, then charge to them 9 sec later. Each image inflicts 8249 Physical damage and applies Touch of the Night to all players in their path, removing Imprinted Safeguards.
Read more on wowhead.com