Updated coordinates. Edit
The header only lists one set of coordinates. There are 4 distinct, never moving, places where they spawn. Since someone doesn't want the info added to the main article, I'll put it here so maybe it will help someone.
There are 4 places where they spawn, all in Blade's Edge Mountains.
1. [27.42, 68.55] 2. [31.77, 63.80] 3. [33.42, 51.83] 4. [28.80, 46.50]
There are 6 mobs at each spawn point.