I don't have the exact details of the 'wowhead most sad story'. However, in World of Warcraft, there are often stories of redemption that are also tinged with sadness. Maybe it's about a character who has done a great wrong in the past and is now trying to make amends. But the price they have to pay for their past mistakes is so high. They have to face the scorn of others, and they might have lost so much in the process of trying to atone that it becomes a very sad story.
Since I'm not certain which story it is, I can only guess. It could be a story about a race that was nearly wiped out. The survivors are left with the memories of their once - great civilization and all the friends and family they've lost. They now struggle to survive in a world that has become so hostile to them. Every day is a reminder of what they've lost, and that's really sad.
Sorry, I really don't have enough information to share details. Maybe it's about a tragic love story between two in - game characters that was cut short by some evil force.