Spawned today on the Mischief server, during the Planes of Power expansion, at coordinates Y: 729, X: 536, Z: -568. Basically top of the tower that is in the Northwest of the zone.
Posting here to confirm this to be correct. I had him spawn tonight at this exact location (top of the undead tower, southernmost "wing"). Took many hours of killing PHs on roughly an ~18m timer (estimated 50+ PHs killed) to get him to spawn, but he indeed spawned exactly here. Hope this is helpful for other TLP Hunter achievement hunters, who are working on it pre revamp.
When I came to the Hole last night with my rogue and 2 friends, we saw this guy at the entrance. First we thought somebody had pulled him there somehow and that he wouldn't return if he had died. He's a nasty mob for a lvl 46 rogue, lvl 48 warrior and a lvl 48 cleric, but we managed to zone out.
About 10 minutes after we had zoned, it came at us again. This time we wiped trying to kill it and we decided to log to our mains to get it out of our way. We also had a revenant, which we killed too. But first we timed his appearance.
The revenant roamed the entrance every 30 minutes, Irslak every 10. I don't know what his respawn time is supposed to be, but he didn't come back after he died. The revenant did though, which kinda spiced up our evening. We saw it coming from the dropoff, he probaly does still spawn in the undead tower and just floats his way to the entrance.
I don't know if this is a permanent change or just a temporary bug, but if it is young groups will have to pay much more attention hunting here :-)
We have killed him numerous times and each time seems random as to what he will drop but the only consistency has been its always Withered leather be it bracer, sash etc.