Suggestions and actual rate:
(changes in italics)
Politoed @ Leftovers
Ability: Drizzle
EVs: 252 HP / 76 Def / 76 SpA / 100 SpD / 4 Spe
Calm Nature
- Scald
- Icy Wind
- Perish Song / Helping Hand
- Protect
This set is pretty much good to go! I can't think of much to improve here. However, consider running Helping Hand over Perish Song in case you ever felt it was too risky. I changed the item to Leftovers since there was an addition I made which needs Sitrus more.
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Swampert @ Swampertite
Ability: Torrent
EVs: 100 HP / 252 Atk / 156 Spe
Adamant Nature
- Waterfall
- Ice Punch
- Earthquake
- Protect
Also good to go, I can't think of much to improve here. Alternative coverage could be obtained in Superpower and Rock Slide over Ice Punch, but I think the current set is more that good enough.
Nessie (Goodra) @ Assault Vest
Ability: Sap Sipper
EVs: 240 HP / 252 SpA / 16 Spe
Modest Nature
- Dragon Pulse
- Sludge Bomb
- Thunderbolt
- Focus Blast
This is the Goodra spread I generally use, and it works well enough for me to suggest it here. Your Goodra was quite similar to mine, I just finalized it's moves and an EV spread for it. Main goal is to hit everything hard and to survive long enough. Here are it's details, in case you were wondering:
>252+ SpA Goodra Dragon Pulse vs. 0 HP / 4 SpD Salamence: 168-200 (98.8 - 117.6%) -- 93.8% chance to OHKO
>252+ SpA Goodra Dragon Pulse vs. 0 HP / 0- SpD Mega Salamence: 174-206 (102.3 - 121.1%) -- guaranteed OHKO
>252+ SpA Goodra Sludge Bomb vs. 164 HP / 4 SpD Assault Vest Ludicolo: 68-80 (38.6 - 45.4%) -- guaranteed 3HKO
>252+ SpA Goodra Focus Blast vs. 0 HP / 4 SpD Mega Lucario: 178-210 (122.7 - 144.8%) -- guaranteed OHKO
>252 SpA Mega Salamence Draco Meteor vs. 240 HP / 0 SpD Assault Vest Goodra: 102-120 (52.3 - 61.5%) -- guaranteed 2HKO
>252+ SpA Life Orb Ludicolo Ice Beam vs. 240 HP / 0 SpD Assault Vest Goodra: 57-68 (29.2 - 34.8%) -- 3.9% chance to 3HKO
>252 SpA Life Orb Hydreigon Draco Meteor vs. 240 HP / 0 SpD Assault Vest Goodra: 133-159 (68.2 - 81.5%) -- guaranteed 2HKO
Scizor @ Lum Berry
Ability: Technician
EVs: 164 HP / 252 Atk / 92 Spe
Adamant Nature
- Bullet Punch
- Knock Off / Quick Guard
- Bug Bite / Feint
- Protect
I tweaked Scizor's spread to balance out it's defenses and offenses a little more evenly. The more prominent changes are in the moves however. You were originally skeptical about Bug Bite, but consider this: Bug Bite bones Cresselia (one of the bulkiest utility pokemon in the current meta) and even has a chance of eating it's Sitrus Berry to heal it's own HP. Alternative to this is Feint, a move that can hit through Protect.
The other optional change I made was adding Quick Guard into Scizor. It's unexpected, and brings a halt to numerous Prankster users and general priority.
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Thundurus (M) @ Sitrus Berry
Ability: Prankster
EVs: 252 HP / 116 Def / 44 SpA / 68 SpD / 28 Spe
Calm Nature
- Thunder Wave
- Thunderbolt
- Hidden Power [Ice]
- Taunt
I have avidly used Rotom-W in the current VGC meta. I've come to this conclusion that unlike in singles, Rotom isn't the pokemon you can just slap on to any team and make it work at top level. For example on this team, Rotom despite being an Electric type cannot conquer Charizard-Y, because it's Water typing left in vulnerable to Charizard's nuclear Solar Beam. Henceforth, Thundurus is your man here, over good ol' Washington.
This particular set is Aaron (Cybertron) Zheng's set, down to the T. It's the Electric type that is going to check Charizard-Y and stand for the general speed control of your team. Imagine a situation where Politoed is gone, and you need that Swampert (or any other team member) to pull off a sweep. However it isn't fast enough. Thundurus' T-Wave helps exactly with that. Taunt is always a nice addition to any Thundurus.
The EVs,
- survive a Stone Edge from Adamant 252 Atk Landorus-T
- survive a Life Orb Draco Meteor from Modest 252 SpA Hydreigon
- outspeeds positive nature base 70s like Breloom.
OR
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Terrakion @ Focus Sash
Ability: Justified
EVs: 252 Atk / 252 Spe / 4 Def
Jolly Nature
- Close Combat
- Rock Slide
- Poison Jab / Double Kick / Zen Headbutt
- Protect
Terrakion is a favorite in rain teams because of his ability to eliminate Charizard-Y and Ferrothorn, while still being a pretty stubborn fighter outside rain. It works best with it's simple vanilla spread. You have choices for coverage moves: you could opt Poison Jab to give those slow Fairy types the surprise of their lives, Double Kick to bump through Substitutes and Sashes, or Zen Headbutt to deal with Venusaur and Amoonguss. People also run Earthquake, however it is much more risky.
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Talonflame @ Life Orb
Ability: Gale Wings
EVs: 252 Atk / 92 SpA / 164 Spe
Naughty Nature
- Brave Bird
- Overheat
- Swords Dance / Will-O-Wisp
- Protect
I understand Armaldo was your niche option and you probably don't want it gone, but think about it. It really isn't helping the team when you have a Scizor with you, and for a Swift Swim user you have your Swampert. If you chose Terrakion then there is even more reason you'd want Armaldo out. I'm sorry but it was somewhat necessary, you have to utilize the few slots you are left with in a rain team wisely.
Talonflame is quite literally the firepower of your team. It's a glass cannon; it was never meant to last. But basically it's there so that you can click Brave Bird to watch the world burn. On this team though, it also rocks Overheat (the reason why those odd 92 SpA EVs are there) which can royally screw defensive pokemon that thought they could take T-flame on, like Landorus-T. 92 EVs so that it can OHKO Mega Metagross outside of rain with Overheat. Rest is all in Attack and Speed.
TL;DR:
Team before rate:
Team after rate: /
Hope you liked this rate, and found it useful!