Check out a recent Quixel livestream with Quixel's Wiktor Öhman explaining the creation process of the WoW Orgrimmar environment.
The project created with the help of Megascans (materials, atlases, and 3D assets), Unreal Engine, Quixel Mixer, Maya, and Mixer. "Creating a fantasy environment was a breath of fresh air having mostly worked on sci-fi and contemporary environments recently. I had an absolute blast working on this, and I hope you enjoy it," said Öhman.
You can learn more about the project here.