Thankfully most of what I said still applies (since I feel the primary function of a core is to allow teammates switch-in opportunities). After an agility with 240 EVs in speed (neutral nature), you'll outrun Deoxys-S, so, basically everything that isn't choice scarved, priority or also speed boosting needs to be in check somehow.omg pardon, Can't believe I said Belly Drum. I meant to say Agility. LOL
Agility Diggersby
You'll more than likely want stealth rocks and maybe spikes to assist in your sweep, so maybe have a preference for rapid spin over defog. Jellicent can spin block and attracts ghost and electric moves, two things Diggersby is immune to. I'm not sure if anyone else has a Jellicent in their core here, but you could replace Tentacruel with Jellicent from mine. It'd give you two lightning rods and would have a weakness to ghost attacks.
Jellicent / Ferrothorn / Togekiss
Jellicent on spin blocker duty and being useful with giga drain, scald, ghost STAB, recover and/or will-o-wisp. Ferrothorn setting rocks and leech seeding things. Togekiss can wish pass and use heal bell, although it may not be as necessary or could use a different set since Jellicent has recover.