I sat in front of the placeholder for 28 minutes and ***POOF** the Froglok Ton Shaman despawned. 30 seconds later she was replaced by...........
a Froglok Ton Shaman...
In Upper Guk: Enchanter; spawns as about 1280, 220, -95
In the Formal Dining Hall: Part of the anniversary task "Lucky 13" (see this quest entry for details).
In the Tower of Frozen Shadow: Part of the third encounter within the Tower of Frozen Shadow anniversary raid (see this quest entry for raid information).