TheWoWDBTo anybody struggling with this guy, or getting seemingly oneshot:
You're probably dying to Unanswered Call, a mid-fight enrage where he fixates you, and if he catches you, you're dead. It has a long cast time and is not interruptible.
However, you just have to kite him. Keep in mind that another one of his spells, Hopeless Curse, reduces movement speed, so you may want to leave yourself extra escape margin.
Elite
Harbinger Ul'thul
The Envoy
The highest voted Wowhead comments for this page. They are community notes, not TheWoWDB comments.
Anyone know what this guy says as he dies?
Something that helped me was killing all the aberrations swirling around before engaging him.
Details
This roster comes from the current game client's data files, so it is not a complete list of every NPC in the game - older world NPCs that are no longer in the modern client are absent.
Community notes from Wowhead · 9 comments
Top 3 shown aboveThe comments below were written by Wowhead users. They are community notes, not TheWoWDB comments. See them in context on Wowhead.
The top 3 are shown in Top Comments above. Read all 9 on Wowhead.
Level and Map Tracking
The game data tunes Harbinger Ul'thul for levels 70 to 80, The War Within content.