Elementalist weapon collection
Probably not, since they are already in the game. Its nice to have thematic weapons seperated a bit too.
I agree that they should- more collections is a good thing.
There should also be a collection achievement for collecting all of the Primordus weapons too, considering they share similarities to the Corrupted weapons.
I have a feeling that a lot of collections were programmed or planned, but the item to unlock the collection was never added to the loot tables.