Even though I have the Glowing Shard in my inventory, I cannot turn the quest in even though the quest dialog with the NPC, Falla Sagewind, even says it’s the only required item.
Did you go to Ratchet and talk to a Goblin first? It’s annoying but you have to go aaaaall the way to Ratchet, talk to one Goblin, then come aaaaall the way back to the top of the Wailing Caverns and talk to the Tauren on the peak.