As these are datamined hotfixes, these may not represent all the changes that are in the game due to datamining limitations.
Patch 12.1 Overview
Mythic+ Dungeons
Blinding Vale
The Blinding Vale buffs a few of the bleeds in the first area, and on the Lightblossom Trinity encounter.
Lekshi's Thornblade periodic damage increased by 100% and duration increased to 12 sec (was 8 sec)
Underbrush Stalker's Thornblade duration increased to 8 sec (was 6 sec)
The Blinding Vale Overview
Altar of Fangs
In Altar of Fangs, many of the abilities have had flags changed to allow, or disallow various methods of damage reduction including immunities, line of sight, and spell reflection.
Rattle can now be immuned.
Septic Spatter can now be immuned.
Envenom can no longer be reflected.
Virulent Whirl now ignores line of sight.
Corrosive Fangs ranged changed to "Vision Range" (was 10 yards)
Noxious Spray now ignores line of sight, cannot be reflected, or immuned.
Altar of Fangs Dungeon
Raid
For the Venomous Abyss raid, it seems that a new flag has been added to some abilities, allowing the damage to be reduced by AoE damage reduction effects like Avoidance.
Stir the Depths now has the "Treat as Area of Effect" flag.
Barbed Bulwark now has the "Treat as Area of Effect" flag.
Vile Flood now has the "Treat as Area of Effect" flag.
The Venomous Abyss
Delve Boss
In the Delve Boss, Warriors could do a significant amount of damage due to Spell Reflection. This appears to now have been changed.
Void Toxin no longer reflectable.
