With the release of Patch 12.0.5, Blizzard announced changes to Mythic Alleria, which were essentially a buff, due to fixing an immunity strategy. While Blizzard did nerf the damage of the ability, it was only by 10%. This low number almost certainly made the encounter harder, and this was the week after the Hall of Fame closed when the raid usually receives nerfs.
It seems that Blizzard has heard this feedback, as the latest hotfixes nerf the damage of Gravity Collapse again.
Gravity Collapse damage reduced by another 10%
This should bring the damage down to 189k per snap, from the original 234k.
