I find it rather unrewarding to fight these enemies. I still DO but I feel like it’s just for EXP instead of stopping the corruption or for any chance of a drop. Maybe there is some other thing I may be missing?
Afaik they can’t drop aether crystals, shards or clusters. I have never seen them drop any of them, they only come out of the crystal groups that don’t morph into something deadly. 
Dunno about crystals, but they can drop shards and clusters.
Hmm news to me, I would think if they can drop shards and clusters it makes sense for them to drop crystals too…