On Mythic Difficulty, the Auras associated with each phase are permanent, but grow weaker after Velhari transitions into the next phase. So, for example, a raid group may spend a long enough time in the Oppression phase to reach 60k damage on movement from the Aura of Oppression, but once they push Velhari to the Contempt phase, the Oppression damage will rapidly taper off. Players will still be penalized for moving for the rest of the fight, but the damage will be much weaker.
Similarly, after pushing Velhari into the Malice phase, the Aura of Contempt remains, but players will gradually be allowed to heal to a higher health percentage as the Malice phase continues. The Aura of Oppression will also still remain in a very weak state, but damage from movement will be affected by the Aura of Malice, so it is even more important for players to minimize movement during the final phase.
The Edict of Condemnation ability is empowered on Mythic difficulty, reducing its target's movement speed by 70%.
This means that the Heroic mode strategy of having the Edict target run into melee or a designated stack point is unlikely to work
The raid can instead run to the Edict target, or players can Leap of Faith the Edict target onto a stack point
Note that Leap of Faith will cause the targeted player to take one tick of Aura of Oppression damage
The Touch of Harm ability is also empowered on Mythic difficulty, dealing 15% of the target's current health as damage every 2 seconds while the player is debuffed.
The targeted player's health will dwindle quickly under the Touch of Harm effect
Healers will have to dispel Touch of Harm as the affected player's health dips low
The Touch of Harm damage can be absorbed, so Discipline Priests with Clarity of Will can prevent a lot of this damage
This extends the amount of time that throughput healers have to heal down the Touch of Harm effect before it must be dispelled
Similarly, Life Cocoon or Guardian Spirit (particularly with the (Spell #159599)) can be used at the start of a fresh Touch of Harm effect to quickly heal off a large portion of the healing absorption shield
Finally, the Ancient Enforcer and Ancient Harbinger adds are more powerful on Mythic difficulty.
The Ancient Enforcer will summon two Roaring Flames fireballs, instead of one, with the Enforcer's Onslaught ability
Both fireballs will travel in the direction the Enforcer is facing, but angle away from each other
Melee DPS must use the 2-second cast time on Enforcer's Onslaught to position themselves out of the path of both fireballs, to avoid Roaring Flames damage and to prevent Searing Blazes from forming
The Enforcer tank should be certain to face the add away from the majority of the raid, especially late in the phase when movement is heavily penalized
Tanks and Melee DPS may wish to use personal damage-reduction cooldowns while moving out of the way of the Roaring Flames
The Ancient Harbinger's Impatience reduces cast times by 20% per stack, rather than 10%