After looking at the rest of the team, I think what we need to round it off is either a secondary special sweeper, for when you can't afford the turn to have Slowking set-up, or a phazer to help shuffle opponents around while maintaing offensive presence.
LO Magmortar is still a viable option, but in terms of special sweeper, I think a better candidate might be Haunter.
Haunter@Life Orb
Modest
252Sp.Atk, 252Spd, 4HP
~Substitute
~Shadow Ball
~Sludge Bomb
~Thunderbolt/Giga Drain/HP Ground
Haunter not only provides an impressive special movepool, but also has multiple opportunities to switch in thanks to its typing and Levitate. It also functions as a spinblocker, as rare as Rapid Spin may be. The fourth move is really up to preference. Thunderbolt hits the Flyers hard, Giga Drain wastes Quagsire, while HP Ground takes down Magneton.
As for the phazer, while Throh is a very tempting choice due to his bulk, I'm hesitant because of the prevalence of Flying and Psychic right now.
Instead, I'll go with:
Luxray@Leftovers
Intimidate
252HP, 252Def, 4Spd
~Roar
~Volt Switch
~Substitute
~Superpower/Rest/HP Grass
IntimiRay can come in on a good portion of physical attackers not carrying EQ, Intimidate them, and shuffle with Roar, hide behind a Sub, or Volt Switch to maintain momentum. The fourth move has a few options. Superpower is strong even without investments in Atk thanks to that huge base ATK set, and does a number to Magneton and Miltank. HP Grass is solely for Quagsire and Stunfisk who otherwise threaten to come in for nearly free thanks to a resistance to SR. Rest gives Luxray longevity, and Intimidate allows it to serve a use even while sleeping.
