I always quite enjoyed being able to find the pokémons that I should expect from certain environments (insects in forests, etc..) but Dreepy's spawn location really doesn't seem to match the pokédex entries from the main games :
After being reborn as a ghost Pokémon, Dreepy wanders the areas it used to inhabit back when it was alive in prehistoric seas.
In the evening, groups of Dreepy will fly at high speeds over the ocean and poke at Pokémon in the water for fun.
It has a habit of biting at Clauncher even though it doesn't feed on them. This is said to be vestigial behavior from when Dreepy was alive.
I understand that this is far from being a priority, but currently it is set to spawn only in Savannas and Evil biomes which seems a bit unexpected for me.
As always, thanks to every member of the staff for this great mod.