I do see hawlucha being a good partner for camerupt, although I don't think ferrothorn is a good partner. Ferrothorn offers meh type synergy, and also gives you two really slow mons on one team. This increases your greninja weakness, because hp fire nukes ferrothorn, and hydro pump for camerupt. I think band talonflame could also make a decent partner because it takes care of greninja, beats keldeo which threatens camerupt, and can also clean up with camerupt acting as a rotom-w magnet. Although they have pretty bad synergy, talonflame's main counters : rotom-w, tyranitar, and heatran, all happen to take a lot from camerupt's attacks, and as someone said rotom-w takes over 40% from fire blast, meaning that if it is weakened enough, talonflame can often sweep.
but yeah I'm just theorymonning