Pacified Aurora Knight Boss Mob has to look into.
If he get the affix "Regeneration" hes is almost not to beat with his minions Hierophant of the Searing Song.
He gets too much healing through active healing spell from his minions, the passive healing from the affix and his immunity (shield) that give him time to heal up/get healed, in this particularly variation of the Boss.
If he and/or his minions gets some other affix as well like, "Tough", "Unstoppable" or other defensive affix hes immortal for almost every build.

Please look into his kit and that of his minions if this amount of healing and defensiv skills is needed/ tune thoes numbers.

You must delete the Regeneration of the Boss Monster.

Don't let the boss monster summon his minster.