I can confirm that if he is lost for whatever reason, someone has to drop quest and get it again. We got to Oracle and hailed her, someone else was pulling imps and got the blighted glog. They dragged him out of tunnels away to the south and he depopped somewhere. After waiting about 45 mins killing imps with no respawn only one of us dropped the task (me). Once I hailed Oracle again, the blighted glog immediately respawned and we promptly killed and all got our drops.
well i found out there is no respawn timer its a triggered spawn from hailing the oracle and if you dont get update from exploreing before killing the imp dont worry the next step is to loot the corpse not kill the imp so u can explore and then loot i realized that after the corpse rotted while i waited for 2 hours for respawn that never came.
so far over 30 min the prev corpse has rotted away and still no repop i was to quick to pull him before i noticed i needed to enter his little cave to get an update before killing him so i pulled him out killed him and noticed when i looked what was needed next and saw i didnt get update so sitting here waiting for repop ill get it timed