I'm not sold on Tatalia -- the RoE campaigns make it clear that Erathia owns and occupies part of that swamp -- but the idea that Krewlod assets were merged into other areas of the game because of a time crunch is actually pretty possible.
It would explain, among other things, why Necromancers occasionally summon goblins. That's the kind of bug that can easily be created by hurriedly merging assets.
The fact that there are Goblins as peasants in Deyja isn't quite enough, though, as Harmondale has a goblin population, even if it's hostile -- showing that Goblins groups are either nomadic by nature or that the conflict between Krewlod, Tatalia, and Erathia in RoE created a lot of refugees. And I would not put it past Deyja to accept permanent Goblin settlements (RoE establishes that they breed like rabbits, if growth and the fact there are two Goblin creature tiers is any indication) with the intent of harvesting them occasionally for raw materials -- shepherds and sheep, if you will.
Far too many people speak their minds without first verifying the quality of their source material.