I can see the reasoning behind your frustration. However, just because you have paid to have early access to some pokemon, doesn't mean that they will appear on a very common level. Granted, they are hard to find. The basic reason for that is that we compiled around 400 into 2 main regions and a few custom island & areas. Hence where the rarity is formed.
Spawn rates are still incomplete, imbalanced even in some areas. This is why there is a "everything about spawns" sub-forum in the bug resolution center. Which can be found here : https://pokemonrevolution.net/forum/viewforum.php?f=85
I have already compiled a report about Shellder and Staryu.