Blizzard is nerfing Mythic Raszageth with the weekly reset in each region.

(Source)

Vault of the Incarnates

[With weekly restarts] The Hall of Fame (Horde) for Vault of the Incarnates has now been filled with the first 100 guilds to defeat Mythic Raszageth. Congratulations to all players who earned a spot in the annals of raiding history this season!

[With weekly restarts] Players from different servers may now group together in Vault of the Incarnates on Mythic difficulty.

Raszageth

Heroic

[With weekly restarts] Health reduced by 5% on Heroic difficulty.

[With weekly restarts] Reduced the rate that Vault Integrity drains during Intermission: The Primalist Strike on Heroic difficulty.

[With weekly restarts] Tempest Wing periodic damage reduced by 20% on Heroic difficulty.

[With weekly restarts] Volatile Current damage reduced by 15%.

Mythic

[With weekly restarts] Reduced the push effect of Hurricane Wing on Mythic difficulty.

[With weekly restarts] Flamesworn Herald’s Flame Shield now absorbs 45% (was 55%) of its maximum health on Mythic difficulty.

[With weekly restarts] Frostforged Zealot’s Shattering Shroud now absorbs 20% less healing on Mythic difficulty.

[With weekly restarts] Stormseeker Acolyte’s Ascension now increases by 150% (was 300%) on Mythic difficulty.

[With weekly restarts] Tempest Wing periodic damage reduced by 20%.