I think that crobat with his super speed and having Hypnosis, Nasty Plot and Taunt in its move list is the perfect counter to Ferrothorn and Foretress. 1 Nasty Plot and thenyoou can taunt it but Crobat already has a good +450 SpA and Heat Wave in its moveset. Bye bye steel starter.
Dark pulse+1 Nasty Plot break with Taunter Azelf.
Sludge Bomb is the Stab move to complete the Sweeper moveset.
With this crobat at the begining of the battle only Blissey and priority move users can stop it