In addition to what Boubou said, bear in mind that even with the buff active, not all of the goblin types are doubled, and that’s covered in the announcement…
https://us.forums.blizzard.com/en/d3/t/double-treasure-goblin-buff-season-22/26709
There are a few important details to keep in mind with this effect:
- This does not affect goblins encountered via Bandit Shrines, Goblin “Rift” packs, or in the Realm of Greed.
- Duplicate Whimsydale portals created by the Rainbow Goblin will enter the same instance of Whimsydale.
- The Insufferable Miscreant is not affected by this buff; this is intended.