Why did I say Magmortar's broken, while Medicham is not?
Magmortar has the capability to be far more unpredictable than Medicham. Medicham, you KNOW is going to use Physical attacks, and generally, you have a basic idea of what type. The predictability of Medicham is far larger than Magmortar.
Magmortar's also FAR bulkier than Medicham, and is far less predictable, making a fearsome combination. Magmortar can attack physically, or specially.
Medicham's been in NU since day 1, and, while it's been powerful, it's not been smashing the teir, or forcing every team to use it, or pack a counter. Magmortar is either on every team, or forcing every team to run Slowking, who's a check only. That sort of centraliastion in the metagame seems broken to me, especially when the best NU can muster is a check that can be 2HKO'ed by one of Magmortar's most common moves.
Medicham has priority, sure, but it dosen't have STAB, or Technician, so it's actually quite weak priority, even with such a high attack stat, BP 40 isn't killing much.
As for Slowking, maybe it is like Venasaur, but the point is, without the broken pokemon in the metagame, especially Magmortar and Espeon, Slowking will be even harder to take out, and that's why I feel it's a POSSIBLE suspect. But only after those 2 are long dead and buried. Skuntank's the same, not much can stand up to it's Sucker Punches and Persuits, and be in a state to fight again, while it's not 'Broken' now, it's more like Scizor in OU, it may be broken with the removal of certain broken pokemon.
Also, Miltank's OK as a lead. How's it Taunt bait, when few common leads outspeed it? It has the fastest rocks in the Teir, and is perfectly capable to coming in later and providing team support. A defensive Support Militank would make a decent lead, to bring back mid game, and wall, or use Heal Bell, or spread Thunder Waves.