I do have a goby paired up with the shrimp... I guess he was cleaning house and the crab got in the way... I had two big snails and they were great until they fell onto their backs and died.I doubt it. Pistol shrimps are mini bulldozers. Always moving sand and making caves. You should pair it up with a goby. I wouldn't worry about your hermits.
Hermits are useless anyways, better off with trochus snails.
-dan