
First, Quagsire isn't a really viable pokemon on Doubles, since it's way too passive and Gastrodon is just way better. Gastrodon, for example, could work on teams that are weak to water-types, absorbing its attacks because of Storm Drain, or as a way to lure some pokemon like Garchomp and Heatran. Gastrodon would work well paired with Scizor or Heatran since it can check pokemon that both have trouble against, like the aforementioned Heatran and Garchomp.
But using Quagsire, doesn't allow you to KO Garchomp and needs some investment to KO Heatran, while also being less bulky and not having Storm Drain as an ability. The access to Toxic could be a reason to use Quagsire tho, but on the majority of teams Gastrodon would be way better.
If you still want to use Quagsire this is the spread that I'd use (you can put some EVs on Sp Attack), keep in mind that it can't KO Garchomp and it can be easily overwhelmed.
Quagsire @ Sitrus Berry
Ability: Water Absorb
EVs: 252 HP / 4 SpA / 252 SpD
Calm Nature
IVs: 0 Atk
- Scald
- Ice Beam
- Toxic
- Recover
Garchomp works on teams that have a lot of immunities to Earthquake, with partners such as Rotom-W, Togekiss and Latios, so I'd replace it for Latios. Latios is probably the best pokemon on the tier right now, threatening opposing Latios and spamming powerful Dracos on everything that isn't Togekiss. It supports its teammates with Tailwind and checks Breloom, since you're using Quagsire.
Latios (M) @ Life Orb
Ability: Levitate
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Draco Meteor
- Psychic
- Tailwind
- Protect
Since Breloom is really weak to Latios and Togekiss, Raikou is a nice option being able to check really well Togekiss and at least soft check Latios with access to Snarl. Breloom benefits from Latios's Tailwind being really annoying to deal with.
Breloom's set should have Protect and Raikou can be offensive, but in this team an utility set with Snarl looks better.
Breloom @ Focus Sash
Ability: Technician
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Spore
- Mach Punch
- Bullet Seed
- Protect
Raikou @ Sitrus Berry
Ability: Inner Focus
EVs: 252 HP / 4 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Thunderbolt
- Snarl
- Volt Switch / Reflect
- Protect
For the last two slots I don't think having double Steel would be good, since it could stack a lot of weaknesses and they don't have a lot of synergy. So I thought about two teams using those 4 pokemons and 2 other.
Heatran has a problem dealing with Garchomp, Tyranitar, Latios, Breloom and Hitmontop and Nasty Plot Togekiss can deal with them. It will still be weak to some pokemons like Manaphy, Rotom-W and even Rock Slide Tyranitar, but Breloom and Quagsire can deal with them.
Heatran @ Leftovers
Ability: Flash Fire
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Heat Wave
- Earth Power
- Substitute
- Protect
Togekiss @ Scope Lens
Ability: Super Luck
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Nasty Plot
- Dazzling Gleam
- Aura Sphere
- Roost
I'm not sure if Scizor fits well with Breloom, but I'd try Entei as a partner. It completes the Water/Grass/Fire core and can threaten Heatran with Bulldoze while apreciating Scizor checking Latios and Tyranitar.
Scizor @ Metal Coat
Ability: Technician
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Swords Dance
- Bullet Punch
- X-Scissor
- Protect
Entei @ Sitrus Berry
Ability: Inner Focus
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Sacred Fire
- Bulldoze
- Extreme Speed
- Protect
