You're supposed to run around with a Spirit Hunter companion and summon Veneratus. But nothing happens for the 10 minutes you have the Spirit Hunter Companion.
Yesterday i tried to run the quests myself for about an hour or so - no luck.
Today i tried running the quest with a full group for about 45 minutes - no luck.
Have anyone done this quest properly? In that case please lend a helping hand. :)
Edit #1: Been asking around. It seems to have worked for some people, but they report that he "bugs out", stands still and repeat his script over and over.
Edit #2: OKAY, IT WORKS. LISTEN UP:
At the coordinates 31,57 (exactly) aka left to the big gate of the alter. Go there, maybe kill a demon or two and he should spawn. Happened to me and a friend just recently.
He spawned after I killed 3 mobs, that's how it's supposed to work. Just keep killing mobs in the area until an emote comes and he spawns, like the quest in Barrens. Other private servers where he has a static spawn are non-blizzlike.