today I ran the dungeon Black Rook Hold on Mythic in order to get the transmog Fel-Hammered Greaves from the world quest reward. I killed Kelorn Nightblade and then Dantallionax, have been credited for killing both but the world quest will not complete
yesterday I had a similar issue with the world quest Liskanoth. I killed the boss, got the loot but the world quest did not complete