Greninja @ Life Orb
EVs: 252 Sp. Atk, 252 Speed, 4 HP
- Surf/ Hydro Pump
- Exstrasensory/ Ice Beam
- Dark Pulse
- HP Fire
HP Fire is a good option in order to deal with Scizor/Ferrothorn/Forrtress. Surf STAB might not do enough for Scizor, and it definitely won't be doing anything to Ferrothorn. The good thing about HP Fire is that Protean will change type to Fire, meaning Fairy will be not very effective as a result.
Some moveset choices will be down to personal preferences. Surf or Hydro Pump, depending if you want accuracy or power. Extrasensory or Ice Beam for coverage. To be honest, Psychic doesn't cover much apart from Fighting and Poison, and with Protean, Greninja will no longer be weak to fighting (because you won't be using a Dark move against a fighting Pokemon). Then again, with HP fire, Ice Beam could be redundant. Surf will cover Landorus & Gliscor, so the main worry there is Thundurus and Tornadus. Again, personal choice and dependant on the rest of your team.
Life Orb does sap health, but I think Greninja can sweep easily because of its great speed, and the fact that all moves will receive STAB due to Protean.