Crustle is lookin' pretty interesting and IMO it actually might have its place in OU as an offensive lead using Custap and Sturdy. I think I'm going to try it out in conjunction with my favorite sweeper: Dragonite or Gyarados.
I myself have used Crustle in OU, and it's proven to be a fine spiker.
It has its place as a Spiker/Rocker on HO teams. It's good at doing the job and it does it quite well thanks to Sturdy. Also, Custap Berry is cool. Pretty good spiker if you ask me, only Smeargle can hold the same honor.
Also, off topic, but when I think of Donphan, I always think "Lol why is this thing OU?"