High Inquisitor Whitemane

Cathedral
Unlock the Cathedral and clear the courtyard, then the church interior and side aisles before approaching Mograine. Visit Fairbanks in the concealed chamber on the right-hand side before starting the altar encounter. Leave the church clear of Scarlet Abbots for the sleep and resurrection sequence with Whitemane.

High Inquisitor Whitemane
Scarlet Commander MograineElite HumanoidElite HumanoidDefeat Mograine first, survive Whitemane's Deep Sleep, then regain control of both enemies after Scarlet Resurrection.
Abilities

Deep Sleep
Puts nearby enemies to sleep for up to 10 seconds. Any damage caused will awaken them.
Restore the group's health before Whitemane's sleep phase. Healing and tank control can pause until players wake.

Scarlet Resurrection
Scarlet Resurrection brings Mograine back. Prepare to collect both enemies and continue the fight after waking rather than treating his first defeat as the finish.

Heal
Calls upon Holy magic to heal an ally.
Reserve an interrupt for Whitemane's Heal, especially after Mograine returns.

Power Word: Shield
Remove Whitemane's Power Word: Shield with an offensive magic dispel when available, then continue focusing her.

Holy Smite
Smites an enemy, inflicting Holy damage.
Cover Holy Smite's targeted Holy damage while keeping an interrupt available for Heal.

Hammer of Justice
Stuns the target for 5 seconds.
Mograine's Hammer of Justice stuns its target. Keep the tank healthy before a stun prevents active responses during the paired phase.

Retribution Aura
Melee strikes against Mograine can return Holy damage through Retribution Aura; healers need to watch the attackers as well as his melee target.

Crusader Strike
Crusader Strike increases its victim's Holy damage taken. Cover that target carefully while Whitemane is also dealing Holy damage.
Tank- Take Mograine first and be ready to regain control of both enemies after Deep Sleep and Scarlet Resurrection. Account for Hammer of Justice when establishing control again, and use protection while Crusader Strike increases your Holy damage taken.
Healer- Restore health before Deep Sleep removes your ability to act. On waking, cover Mograine's tank through Hammer of Justice and Crusader Strike, while watching melee attackers taking Retribution Aura damage.
Damage- Defeat Mograine first. After the resurrection, focus Whitemane, interrupt Heal and remove her magic shield when possible. Finish Mograine again after Whitemane falls.