My original team really didn't work, as it would gain momentum, but quickly falter. I've been going over Smogon, and have rebuilt my team, maintaining none of the original members.
LEAD
Celebi
Timid Nature
Occa Berry
40 HP / 252 SpA / 216 Spe
~Stealth Rock
~Leaf Storm
~Earth Power
~U-Turn
Stealth Rock is Celebi's best option for supporting the team in a lead position. Leaf Storm decimates Pokemon such as Swampert, Aerodactyl, Tyranitar, and Gliscor, while Earth Power 2HKOes both Metagross and Heatran. U-turn provides momentum for my team, allowing Celebi to scout the opposing team, and help against Azelf leads. It can also cause more entry hazard damage because my opponent will have to switch in a new Pokemon to handle mine.
PHYSICAL TANK
Swampert
Careful Nature
Leftovers
252 HP / 4 Def / 252 Sp.D
~Curse
~Waterfall
~Earthquake
~Avalanche
A bit of a spin-off of the few sets on Smogon, combining the elements of the Tank, Curse, and Sweeper sets. Curse up for Attack and Defense boosts, then continue to sweep. Earthquake provides sufficient STAB and destroys Heatran, whom is a nuisance for Celebi. Waterfall also provides STAB and helps fend off Hippowdon and Mamoswine, along with Aerodactyl. Avalanche deals with Gliscor leads that Celebi U-Turns away from, along with Flygon and Dragonite.
SPECIAL SWEEPER
Gengar
Hasty Nature
Life Orb
4 Atk / 252 SpA / 252 Spe
~Shadow Ball
~Thunderbolt
~Focus Blast
~Explosion
Life Orb Gengar is a fearsome sweeper that has few true counters. With great Special Attack and Speed, great type coverage, as well as three immunities, Gengar is capable of dealing heavy damage to almost any team. Shadow Ball and Focus Blast give Gengar complete type coverage and hit some of the metagame's top threats for super effective damage. Focus Blast always OHKOes max HP Tyranitar in sandstorm, 2HKOes most Snorlax, and always OHKOes min HP Heatran. Thunderbolt offers a quick OHKO against Gyarados and 2HKOes max HP Suicune. Finally, Explosion allows Gengar to go out with a bang and possibly defeat Blissey.
MIXED SWEEPER
Infernape
Hasty Nature
Life Orb
200 Att / 200 Sp.A / 108 Spe
~Close Combat
~Flamethrower
~Grass Knot
~Stone Edge
A set from Serebii. A pure mixed sweeper set-up. I chose Expert Belt over Life Orb due to Gengar. Close Combat is a reliable move that deals a large amount of damage. Flamethrower over Flare Blitz, mostly due to the recoil, and to make the set a pure mix. I do not do Hidden Power, so Grass Knot and Stone Edge are for me. Both do a good deal to types that put Infernape in danger.
STALL / WALL
Skarmory
Impish Nature
Leftovers
252 HP / 240 Def / 16 Spe
~Spikes
~Whirlwind
~Roost
~Brave Bird / Drill Peck
Skarmory's trademark set, known for providing excellent support and walling an astounding number of physical sweepers, such as Gyarados and Metagross. With Brave Bird, Skarmory can take a decent chunk out of anyone who doesn't resist it, but I'm not sure whether to swap it with Drill Peck. Which is better? Roost removes any damage Skarmory may have taken. As a bonus, it also removes Skarmory's Flying-type for the turn so he takes less damage from Rock-, Ice-, and Electric-type attacks. Spikes causes trouble for any grounded Pokemon, as they lose 25% of their health every switch-in with three layers. Whirlwind removes any stat boosts the opponent may have obtained, and forces in another Pokemon to take damage from Spikes and other entry hazards.
SPINNER AND PRIORITY
Donphan
Adamant Nature
Focus Sash / Life Orb
172 HP / 252 Atk / 84 Spe
~Earthquake
~Assurance
~Ice Shard
~Rapid Spin
Not the common choice, but it provides bulk. Salac berry boosts speed when necessary, but Enigma Berry will restore up to a maximum of 96 damage, which could be vital. Earthquake for STAB, and Donphan's best hit. Assurance covers other spin-blockers and levitating ghost-types. Ice Shard for priority, allowing a quick, powerful, and super-effective hit on flying opponents like Zapdos. Rapid spin clears away any sets of Spikes or Stealth Rock on my field, keeping my Pokemon safer. If you can suggest a better Spinner that does not overlap any typing above, go right on ahead.
LEAD

Celebi
Timid Nature
Occa Berry
40 HP / 252 SpA / 216 Spe
~Stealth Rock
~Leaf Storm
~Earth Power
~U-Turn
Stealth Rock is Celebi's best option for supporting the team in a lead position. Leaf Storm decimates Pokemon such as Swampert, Aerodactyl, Tyranitar, and Gliscor, while Earth Power 2HKOes both Metagross and Heatran. U-turn provides momentum for my team, allowing Celebi to scout the opposing team, and help against Azelf leads. It can also cause more entry hazard damage because my opponent will have to switch in a new Pokemon to handle mine.
PHYSICAL TANK

Swampert
Careful Nature
Leftovers
252 HP / 4 Def / 252 Sp.D
~Curse
~Waterfall
~Earthquake
~Avalanche
A bit of a spin-off of the few sets on Smogon, combining the elements of the Tank, Curse, and Sweeper sets. Curse up for Attack and Defense boosts, then continue to sweep. Earthquake provides sufficient STAB and destroys Heatran, whom is a nuisance for Celebi. Waterfall also provides STAB and helps fend off Hippowdon and Mamoswine, along with Aerodactyl. Avalanche deals with Gliscor leads that Celebi U-Turns away from, along with Flygon and Dragonite.
SPECIAL SWEEPER

Gengar
Hasty Nature
Life Orb
4 Atk / 252 SpA / 252 Spe
~Shadow Ball
~Thunderbolt
~Focus Blast
~Explosion
Life Orb Gengar is a fearsome sweeper that has few true counters. With great Special Attack and Speed, great type coverage, as well as three immunities, Gengar is capable of dealing heavy damage to almost any team. Shadow Ball and Focus Blast give Gengar complete type coverage and hit some of the metagame's top threats for super effective damage. Focus Blast always OHKOes max HP Tyranitar in sandstorm, 2HKOes most Snorlax, and always OHKOes min HP Heatran. Thunderbolt offers a quick OHKO against Gyarados and 2HKOes max HP Suicune. Finally, Explosion allows Gengar to go out with a bang and possibly defeat Blissey.

MIXED SWEEPER
Infernape
Hasty Nature
Life Orb
200 Att / 200 Sp.A / 108 Spe
~Close Combat
~Flamethrower
~Grass Knot
~Stone Edge
A set from Serebii. A pure mixed sweeper set-up. I chose Expert Belt over Life Orb due to Gengar. Close Combat is a reliable move that deals a large amount of damage. Flamethrower over Flare Blitz, mostly due to the recoil, and to make the set a pure mix. I do not do Hidden Power, so Grass Knot and Stone Edge are for me. Both do a good deal to types that put Infernape in danger.
STALL / WALL

Skarmory
Impish Nature
Leftovers
252 HP / 240 Def / 16 Spe
~Spikes
~Whirlwind
~Roost
~Brave Bird / Drill Peck
Skarmory's trademark set, known for providing excellent support and walling an astounding number of physical sweepers, such as Gyarados and Metagross. With Brave Bird, Skarmory can take a decent chunk out of anyone who doesn't resist it, but I'm not sure whether to swap it with Drill Peck. Which is better? Roost removes any damage Skarmory may have taken. As a bonus, it also removes Skarmory's Flying-type for the turn so he takes less damage from Rock-, Ice-, and Electric-type attacks. Spikes causes trouble for any grounded Pokemon, as they lose 25% of their health every switch-in with three layers. Whirlwind removes any stat boosts the opponent may have obtained, and forces in another Pokemon to take damage from Spikes and other entry hazards.
SPINNER AND PRIORITY

Donphan
Adamant Nature
Focus Sash / Life Orb
172 HP / 252 Atk / 84 Spe
~Earthquake
~Assurance
~Ice Shard
~Rapid Spin
Not the common choice, but it provides bulk. Salac berry boosts speed when necessary, but Enigma Berry will restore up to a maximum of 96 damage, which could be vital. Earthquake for STAB, and Donphan's best hit. Assurance covers other spin-blockers and levitating ghost-types. Ice Shard for priority, allowing a quick, powerful, and super-effective hit on flying opponents like Zapdos. Rapid spin clears away any sets of Spikes or Stealth Rock on my field, keeping my Pokemon safer. If you can suggest a better Spinner that does not overlap any typing above, go right on ahead.