A day has passed since Heart of Fear opened and still no heroic kills - but things might be changing with an incoming nerf:
The Heroic Zor'lok encounter is currently more difficult than intended. While we prefer to avoid changes to encounters in the midst of progression, we would like to fix a few quality of life issues and make some targeted balance changes that do not invalidate the efforts that guilds have put into learning the encounter so far. Later today a hotfix will make the following adjustments:
Zor'lok's Echoes will pause briefly before beginning to cast Song of the Empress.
Zor'lok's berserk timer has been increased slightly.
Zor'lok will no longer summon Echoes of Force and Verve during the final phase of the encounter.source