In that case, give Kartana a Choice Scarf for a Revenge Killer, Choice Band for Wall Breaker, or Fightinium Z for a Z-Nuke. :P
Ferrothorn Should be able to tank Earthquake, although, it usually uses more Defense EVs. :P
Mega Scizor will tank a Rock Blast, set up Swords Dance, and then Spam Bullet Punch. Mega Scizor is kinda known for killing non-Fire type Speed Boosted/Fast Sweepers like Cloyster. :P
Also, Cloyster isn't as reusable as Excadrill as it will either have to Rapid Spin and die or Shell Smash, KO, and die. Even then, I'd say a reusable Defoger is more useful than Cloyster just because it can remove Stealth Rocks more reliably and keep your Volcarona safe. :P
Are you sure Focus Sash is the best item For Mimikyu? Even if it gets 2 Sword Dances in, there is still stuff that is faster than it, will take a Shadow Sneak at +4 Atk stages, and will kill it. Also, a lot of people Burn/Toxic Mimikyu rather than doing damage, and then send out Ferro with Leech Seed or Skarmory that spams Roost. While Drain Punch offers good coverage, Shadow Claw with Ghostium Z allows Mimikyu to break through walls like Celesteela and Skarmory that it otherwise wouldn't beat, while Life Orb allows it to sweep more effectively. :P
