Stellar and I agreed this needed a revamp, in the movesets for the most part.
http://www.smogon.com/dp/pokemon/magcargo
[SET]
name: Support
move 1: Lava Plume
move 2: Light Screen / Stealth Rock
move 3: Recover
move 4: Yawn / Toxic
item: Leftovers
nature: Bold
evs: 252 HP / 172 Def / 84 SpDef
[SET COMMENTS]
<p>Magcargo has very unfortunate typing, but a rather good support movepool that shouldn't be overlooked. Lava Plume is the main option on this set, due to its 30% chance of burning the opponent, but Flamethrower can be used if you want an extra kick in power. Magcargo has the choice between Light Screen and Stealth Rock here. Light Screen boosts Magcargo's decent Special Defense while also benefitting the entire team. Stealth Rock is useful support against Flying-types such as Articuno. Recover is possibly one of the best moves Magcargo has access to, being able to recover 50% of its health without the use of Rest, which will make it one bulky Pokemon to take down if not prepared for it and allows Magcargo to take hits from threats such as Swellow and Leafeon in UU. Yawn helps cause switches to rack up Stealth Rock damage or puts a counter to sleep, and is a useful pseudo-phazing move in general. Toxic can be used over Yawn, because it gives Magcargo a way to wear down opposing sponges like Gastrodon and Quagsire, who would usually switch into Magcargo with impunity.</p>
<p>With 172 EVs invested in Defense, its Defense reaches a stat of 350, allowing Magcargo to survive some Fighting-type attacks from Pokemon like Hitmonlee. Thanks to Flame Body, Magcargo has a 30% chance of inflicting a burn upon contact.</p>
[SET]
name: Choice Specs
move 1: Overheat / Fire Blast
move 2: AncientPower
move 3: Earth Power
move 4: Hidden Power Grass
item: Choice Specs
nature: Modest
evs: 176 HP / 252 SpA / 80 Spe
[SET COMMENTS]
<p>Magcargo's often overlooked base 80 Special Attack can be best utilized on a Choice Specs set. Choice Specs boosts Magcargo's Special Attack to a respectable stat of 426. Because Magcargo will usually switch after attacking, it can use Overheat without suffering too much from the two stage Special Attack drop. Fire Blast is a powerful STAB option that can be used in place of Overheat. Fire Blast allows Magcargo to continue attacking without the immediate need to switch out. AncientPower is Magcargo's best option against Altaria and has the extra bonus of possibly boosting Magcargo's stats. Earth Power, when paired alongside Overheat and Ancient Power, gives Magcargo complete type-coverage in UU. Earth Power allows Magcargo to more easily dispose of Probopass and Bastiodon. Hidden Power Grass deals massive damage to Quagsire and Gastrodon, two Pokemon that take relatively little damage from any of Magcargo's other attacks. 212 HP Gastrodon is always OHKOed by Hidden Power Grass, meaning Quagsire is also OHKOed.</p>
<p>Max Special Attack is used on this set in order to maximize Magcargo's offensive capabilities. 80 Speed EVs allow Magcargo to outspeed minimum Gastrodon and Quagsire and hit them with Hidden Power Grass before they can retaliate with Water and Ground-type attacks. The remainder of the EVs are placed into HP, allowing Magcargo to take a hit more efficiently with its decent defensive stats. Because Magcargo's HP is odd, it is also able to switch into Stealth Rock four times without fainting.</p>
[Other Options]
<p>Sunny Day allows Magcargo to boost the power of its Fire-type moves while lessening its weakness to Water-type attacks. Explosion allows Magcargo to go out with a literal boom, however its puny base 50 Attack will severely hamper the damage output. Protect can be used in conjunction with Toxic to rack up additional damage while scouting the opponent's next move. Reflect can be used over Light Screen to further boost Magcargo's high Defense. It also has the additional merit of benefiting the entire team. Solar Beam, when used in conjunction with Sunny Day, gives Magcargo a more powerful option against Water and Rock-types. Stockpile is a rather gimmicky option that can be used alongside Recover. It allows Magcargo to boost both its defensive stats simultaneously, similar to Cosmic Power, however the boost maxes out at +3. Will-o-Wisp is a good support option that allows Magcargo to almost always burn the opponent, after factoring in its shaky 75% accuracy.</p>
[EVs]
<p>Maxing out HP on the defensive set is a given. With 172 Defense EVs, Magcargo reaches a Defense stat of 350, allowing it to take hits from common UU Pokemon such as Swellow and Leafeon. The remaining 84 EVs are placed into Special Defense. A handful of Special Defense EVs will go a long way when used alongside Light Screen, which essentially doubles Magcargo's Special Defense.</p>
<p>On the Choice Specs set, max Special Attack greatly increases Magcargo's damage potential. With Choice Specs and 252 EVs, Magcargo essentially has a Special Attack stat of 426. 80 Speed EVs allow Magcargo to outspeed those Gastrodon and Quagsire who do not invest in Speed. Magcargo can then OHKO them with Hidden Power Grass. The remaining EVs are placed into HP, allowing Magcargo to take a hit or two before fainting.</p>
[Opinion]
<p>Using Magcargo in the higher tiers is an obvious no-no. Magcargo's weaknesses to common Ground, Rock, Water, and Fighting-type attacks coupled with its extremely low Speed mean that Magcargo will not survive long. Magcargo is outclassed by Heatran in OU and Camerupt in UU; however, Camerupt does not have Magcargo's useful Normal and Flying resistances.</p>
<p>NU is the tier that Magcargo shines in. With the abundance of Bug, Flying, and Normal-types in NU, Magcargo makes an efficient Pokemon for sponging physical hits. Magcargo still has to worry about its common weaknesses, but they are not as common in NU as they are in the higher tiers. Magcargo's ability to lay down Stealth Rock should also be emphasized in NU, due to the fact that it shaves 50% off Ledian, Beautifly, Mothim, and other Pokemon 4x weak to Rock.</p>
[Counters]
<p>Essentially, any Pokemon that carries a Water or Ground-type attack and has decent Special Defense can be considered a Magcargo counter. However, any physical Pokemon that fall under this description must be wary of possible burn from Lava Plume and Will-o-Wisp. The three Water / Ground-types in UU: Whiscash, Gastrodon, and Quagsire, are the best counters for Magcargo due to their good defensive stats and resistance to Fire-type attacks. Other honorable mentions include Pelipper and Wailord. Calm Politoed is capable of switching in on any of Magcargo's attacks, including Specs Hidden Power Grass, and because Politoed commonly uses special attacks, it does not have to worry about a possible burn reducing its Attack. Politoed also has access to Refresh, allowing it to cure itself of any possible status afflictions. Omastar is able to switch in on a Fire-type attack and OHKO with STAB Surf or Hydro Pump. Omastar must of course be wary of Hidden Power Grass and repeated Earth Powers. Mantine, at most, takes 47% from Choice Specs AncientPower, meaning it can reliably counter the Choice Specs set. Mantine just needs watch out for the rare Hidden Power Electric. Thick Fat Grumpig can switch into and set up on the majority of Magcargo's attacks due to its high Special Defense, but needs to avoid Toxic. Camerupt works well with its immunity to burn, neutrality to AncientPower, and resistance to Fire.</p>

http://www.smogon.com/dp/pokemon/magcargo
[SET]
name: Support
move 1: Lava Plume
move 2: Light Screen / Stealth Rock
move 3: Recover
move 4: Yawn / Toxic
item: Leftovers
nature: Bold
evs: 252 HP / 172 Def / 84 SpDef
[SET COMMENTS]
<p>Magcargo has very unfortunate typing, but a rather good support movepool that shouldn't be overlooked. Lava Plume is the main option on this set, due to its 30% chance of burning the opponent, but Flamethrower can be used if you want an extra kick in power. Magcargo has the choice between Light Screen and Stealth Rock here. Light Screen boosts Magcargo's decent Special Defense while also benefitting the entire team. Stealth Rock is useful support against Flying-types such as Articuno. Recover is possibly one of the best moves Magcargo has access to, being able to recover 50% of its health without the use of Rest, which will make it one bulky Pokemon to take down if not prepared for it and allows Magcargo to take hits from threats such as Swellow and Leafeon in UU. Yawn helps cause switches to rack up Stealth Rock damage or puts a counter to sleep, and is a useful pseudo-phazing move in general. Toxic can be used over Yawn, because it gives Magcargo a way to wear down opposing sponges like Gastrodon and Quagsire, who would usually switch into Magcargo with impunity.</p>
<p>With 172 EVs invested in Defense, its Defense reaches a stat of 350, allowing Magcargo to survive some Fighting-type attacks from Pokemon like Hitmonlee. Thanks to Flame Body, Magcargo has a 30% chance of inflicting a burn upon contact.</p>
[SET]
name: Choice Specs
move 1: Overheat / Fire Blast
move 2: AncientPower
move 3: Earth Power
move 4: Hidden Power Grass
item: Choice Specs
nature: Modest
evs: 176 HP / 252 SpA / 80 Spe
[SET COMMENTS]
<p>Magcargo's often overlooked base 80 Special Attack can be best utilized on a Choice Specs set. Choice Specs boosts Magcargo's Special Attack to a respectable stat of 426. Because Magcargo will usually switch after attacking, it can use Overheat without suffering too much from the two stage Special Attack drop. Fire Blast is a powerful STAB option that can be used in place of Overheat. Fire Blast allows Magcargo to continue attacking without the immediate need to switch out. AncientPower is Magcargo's best option against Altaria and has the extra bonus of possibly boosting Magcargo's stats. Earth Power, when paired alongside Overheat and Ancient Power, gives Magcargo complete type-coverage in UU. Earth Power allows Magcargo to more easily dispose of Probopass and Bastiodon. Hidden Power Grass deals massive damage to Quagsire and Gastrodon, two Pokemon that take relatively little damage from any of Magcargo's other attacks. 212 HP Gastrodon is always OHKOed by Hidden Power Grass, meaning Quagsire is also OHKOed.</p>
<p>Max Special Attack is used on this set in order to maximize Magcargo's offensive capabilities. 80 Speed EVs allow Magcargo to outspeed minimum Gastrodon and Quagsire and hit them with Hidden Power Grass before they can retaliate with Water and Ground-type attacks. The remainder of the EVs are placed into HP, allowing Magcargo to take a hit more efficiently with its decent defensive stats. Because Magcargo's HP is odd, it is also able to switch into Stealth Rock four times without fainting.</p>
[Other Options]
<p>Sunny Day allows Magcargo to boost the power of its Fire-type moves while lessening its weakness to Water-type attacks. Explosion allows Magcargo to go out with a literal boom, however its puny base 50 Attack will severely hamper the damage output. Protect can be used in conjunction with Toxic to rack up additional damage while scouting the opponent's next move. Reflect can be used over Light Screen to further boost Magcargo's high Defense. It also has the additional merit of benefiting the entire team. Solar Beam, when used in conjunction with Sunny Day, gives Magcargo a more powerful option against Water and Rock-types. Stockpile is a rather gimmicky option that can be used alongside Recover. It allows Magcargo to boost both its defensive stats simultaneously, similar to Cosmic Power, however the boost maxes out at +3. Will-o-Wisp is a good support option that allows Magcargo to almost always burn the opponent, after factoring in its shaky 75% accuracy.</p>
[EVs]
<p>Maxing out HP on the defensive set is a given. With 172 Defense EVs, Magcargo reaches a Defense stat of 350, allowing it to take hits from common UU Pokemon such as Swellow and Leafeon. The remaining 84 EVs are placed into Special Defense. A handful of Special Defense EVs will go a long way when used alongside Light Screen, which essentially doubles Magcargo's Special Defense.</p>
<p>On the Choice Specs set, max Special Attack greatly increases Magcargo's damage potential. With Choice Specs and 252 EVs, Magcargo essentially has a Special Attack stat of 426. 80 Speed EVs allow Magcargo to outspeed those Gastrodon and Quagsire who do not invest in Speed. Magcargo can then OHKO them with Hidden Power Grass. The remaining EVs are placed into HP, allowing Magcargo to take a hit or two before fainting.</p>
[Opinion]
<p>Using Magcargo in the higher tiers is an obvious no-no. Magcargo's weaknesses to common Ground, Rock, Water, and Fighting-type attacks coupled with its extremely low Speed mean that Magcargo will not survive long. Magcargo is outclassed by Heatran in OU and Camerupt in UU; however, Camerupt does not have Magcargo's useful Normal and Flying resistances.</p>
<p>NU is the tier that Magcargo shines in. With the abundance of Bug, Flying, and Normal-types in NU, Magcargo makes an efficient Pokemon for sponging physical hits. Magcargo still has to worry about its common weaknesses, but they are not as common in NU as they are in the higher tiers. Magcargo's ability to lay down Stealth Rock should also be emphasized in NU, due to the fact that it shaves 50% off Ledian, Beautifly, Mothim, and other Pokemon 4x weak to Rock.</p>
[Counters]
<p>Essentially, any Pokemon that carries a Water or Ground-type attack and has decent Special Defense can be considered a Magcargo counter. However, any physical Pokemon that fall under this description must be wary of possible burn from Lava Plume and Will-o-Wisp. The three Water / Ground-types in UU: Whiscash, Gastrodon, and Quagsire, are the best counters for Magcargo due to their good defensive stats and resistance to Fire-type attacks. Other honorable mentions include Pelipper and Wailord. Calm Politoed is capable of switching in on any of Magcargo's attacks, including Specs Hidden Power Grass, and because Politoed commonly uses special attacks, it does not have to worry about a possible burn reducing its Attack. Politoed also has access to Refresh, allowing it to cure itself of any possible status afflictions. Omastar is able to switch in on a Fire-type attack and OHKO with STAB Surf or Hydro Pump. Omastar must of course be wary of Hidden Power Grass and repeated Earth Powers. Mantine, at most, takes 47% from Choice Specs AncientPower, meaning it can reliably counter the Choice Specs set. Mantine just needs watch out for the rare Hidden Power Electric. Thick Fat Grumpig can switch into and set up on the majority of Magcargo's attacks due to its high Special Defense, but needs to avoid Toxic. Camerupt works well with its immunity to burn, neutrality to AncientPower, and resistance to Fire.</p>