Sylveon is so so good on Baton Pass teams! Some may prefer Mr. Mime as a CM + BP Fairy-type, since it has access to Soundproof, but Echoed Voice Sylveon is such an excellent (secondary) win condition if an Espeon sweep doesn't pan out.
I can't think of a viable user of Perish Song outside of Celebi or Politoed, and neither are common enough to make Mr. Mime a requirement.
I can't think of a viable user of Perish Song outside of Celebi or Politoed, and neither are common enough to make Mr. Mime a requirement.