With the introduction of Dream World abilities now is as good a time as ever to plan a rain dance team. So let's begin.
EVs: 4 HP, 252 Sp Atk, 252 Spd
With Politoed's Dream World ability being Drizzle it's obvious it should be my lead. The moveset is pretty good in my opinion. Boiling Water is for STAB and the 30% chance of burning is nice. Surf and Hydro Pump is one of those accuracy over power things. Both are goods moves it just depends on what you want. Ice Beam is for Dragon types like Dragonite. Focus Blast is to take out Dark types like say Zoroark.
Ability: Swift Swim
Iem: Life Orb
EVs: 252 Atk, 80 Sp Atk, 176 Spd
Kingdra and alot of other water types are great with Politoed. Considering some of them have Swift Swim as their ability they will be good to have. Waterfall is for STAB and for possible flinching as well as being boosted by the rain. Outrage is for Pokemon that have low physical defense and Draco Meteor is for those that have lower special defense. Dragon Dance just makes Kingdra faster and stronger thanks to the attack and speed boost.
EVs: 192 HP, 252 Def, 64 Sp Def
With Vaporeon's Dream World ability being the same as Manaphy's regular ability there's no way you can keep this Pokemon out. Boiling Water is inflect burn and for STAB. HP Electric is to take care of other water types like say Gyarados. With Wish's new mechcanics it's a great recovery move for Vaporeon. Rest could be a better option because of it's ability but I don't care.
Protect is for letting Wish give Vaporeon some health back.
Item: Choice Band
Ability: Huge Power
EVs: 252 Atk, 4 Def, 252 HP
Azumarill is another great Pokemon that benifits from the rain. Auqa Jet is to Azumarill the ability to hit it's opponet before it can attack. Superpower is good for Azumarill to take out Pokemon that resist Aqua Jet such as Natorrei. Ice Punch is for Dragon types that resist Aqua Jet. Waterfall is their for STAB.
Item: White Herb
Ability: Swift Swim
EVs: 252 HP, 58 Atk, 200 Spd
I found this set to be quite interesting. Shell Break is for rasing it's offenisve and speed stats while lowering it's defensive stats. Thankfully the defense drops are never there thanks to the White Herb item. Then it can use Baton Pass to pass the stat boost to another Pokemon like Kingdra for example. Waterfall is for STAB and to deal with the usual Fire, Rock and Ground types and Ice Fang is for Dragon types.
EVs: 252 HP, 168 Def, 88 Spd
Unfortuantly for Rotom's forms they are no longer Ghost types so they can't get STAB from Shadow Ball like in the last generation. Still the wash form is pretty good as a wall. Thunderbolt is common on most Electric types as they have great special attack. Hydro Pump is for STAB and it's pretty powerful for Rotom. Will-O-Wisp is to deal an instant burn in case Vaporeon or Politoed goes down. Pain Split is for damageing Pokeom that use a recovery move like Recover.
Well that's my Gen 5 Rain Dance team and I hope you enjoyed it. Please feel free to give me your opinions and suggestions to make this team better. I'm thinking of putting Burungeru on this team cause I might need a bulky Ghost and Water type. Might replace Rotom-W for it.