Hello,
When I use the item “Ensorcelled Chorker” and turn into a Ghoul something odd happens. Every so often I will see orange numbers, (like when a pet does damage), show up and will see that an NPC is being damaged. This happens to both friendly NPCs (Scourge) and hostile ones. This has made it impossible to do the quest “Sabotage” as the NPC Malmortis gets killed in one or two of these odd hits.
Hope this helps and can be fixed, I’ve always like this quest line 
.
Edit: I am doing this on an Undead warrior so I don’t have a pet that could be doing the damage.
This is still an issue on the Disclosure quest, where Malmortis dies in two hits. I checked WoWhead and there are reports of this bug going back to at least 2016 and it’s still an issue. I have tried all of the fixes recommended there, and I simply cannot complete this quest. Malmortis just dies before I ever get that far to the invisible pet damage. I’m doing this on a Monk, so I do not have a pet.
Confirming that this is still an issue, making completion of the quest nigh impossible. Combat log shows the damage source as Overlord Drakuru.
This is still an issue. Malmortis dies before he can even get to his second line of dialogue. The ticking orange damage was happening to random scourge throughout the questline (including the friggin gheists you controlled to make collect crystals sometimes) but wasn’t anything more than an annoyance until Disclosure. Level 23 Undead Priest - no pets or anything that would be attacking
STILL an issue! Even running around naked does nothing to stop NPCs from being 2-shotted and the quest uncompletable. Trying to do this on a lvl 47 demon hunter.
I don’t know if it made a difference, but I was able to complete it after about a DOZEN attempts. As soon as I clicked on the coffin I ran away from him and clicked on a geist. As he started his spiel I stayed as far away as possible but still within line of sight and kept targeting other geists that were close to me and running away from him. Finally able to turn in to Drakuru.