It’s not bugged it’s just been changed. After the fight and using Xal’atath Blade on the corpse use the portal in the room to take you to Dalaran. Once in back in Dalaran go to the Alliance or Horde Hold. Go inside and walk upstairs to your right and you will find a portal to the Netherlight Temple. Use the portal and you will find Moira Thaurissan there to turn the quest in. I hope this helps