Damp Rock is preferred on Politoed so that its Drizzle is extended to 8 turns. Lefties recovery will be missed, but this is what Rest is for (yes, it's unreliable, but the sole purpose of Politoed is to set up rain):
-Scald
-Toxic
-Encore/Hypnosis
-Hypnosis/Ice Beam/Rest
Nature: Calm
EVs: 252 HP/4 SAtk/252 SDef
Item: Damp Rock
Ability: Drizzle
What's the deal with Ludicolo's EVs? The aim of rain offensive teams is to hit as hard and fast as you can, so the standard 4 HP/252 SAtk/252 Spe is preferred. Hydro Pump > Scald so that Ludicolo has more power behind it.
For Dragon Dance Dragonite, Fire Punch is weakened in rain. Also, it learns a strong priority move in Extreme Speed:
-Dragon Dance
-Outrage/Dragon Claw
-Earthquake
-Extreme Speed
Nature: Adamant
EVs: 252 Atk/4 Def/252 Spe
Item: Lum Berry/Leftovers
Ability: Multiscale
I dunno how good Heliolisk is, tbh. It's very physically frail, making it prone to priority. I think Mega Ampharos is a good substitute because it's bulkier and still poses a threat with STAB Thunder:
-Agility
-Thunder
-Dragon Pulse
-Focus Blast
Nature: Modest
EVs: 4 HP/252 SAtk/252 Spe
Item: Ampharosite
Ability: Static
Toxicroak really suffered when rain got nerfed to 5-8 turns. It's not that useful anymore and neither is Jellicent now that Knock Off is everywhere. Other rain abusers to turn to are Kingdra, Kabutops, Azumarill, Scizor and Therian Tornadus. Defog Latias also gives team support:
Kingdra:
-Hydro Pump
-Draco Meteor
-Outrage/Rain Dance
-Waterfall/Surf
Nature: Rash/Modest
EVs: 64 Atk/252 SAtk/192 Spe
Item: Life Orb
Ability: Swift Swim
Kabutops:
-Waterfall
-Stone Edge
-Swords Dance/Rapid Spin
-Aqua Jet/Low Kick
Nature: Adamant
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb
Ability: Swift Swim
Azumarill:
-Waterfall
-Aqua Jet
-Play Rough
-Superpower/Knock Off
Nature: Adamant
EVs: 228 HP/252 Atk/28 Spe or 16 HP/252 Atk/240 SDef
Item: Choice Band/Assault Vest
Ability: Huge Power
or
-Belly Drum
-Aqua Jet
-Play Rough
-Superpower/Waterfall
Nature: Adamant
EVs: 92 HP/252 Atk/164 Spe
Item: Sitrus Berry
Ability: Huge Power
Scizor:
-Swords Dance
-Bullet Punch
-X-Scissor/Bug Bite/Brick Break/Knock Off
-Roost
Nature: Adamant
EVs: 248 HP/44 Atk/116 Def/108 SDef or 252 HP/252 Atk/4 SDef
Item: Scizorite/Leftovers
Abiilty: Light Metal/Technician
or
-Swords Dance
-Bullet Punch
-Bug Bite/X-Scissor/Knock Off
-Superpower/Brick Break
Nature: Adamant
EVs: 252 Atk/4 SDef/252 Spe
Item: Scizorite/Life Orb
Ability: Light Metal/Technician
or
-U-turn
-Bullet Punch
-Superpower/Brick Break
-Pursuit/Knock Off
Nature: Adamant
EVs: 248 HP/252 Atk/8 SDef
Item: Choice Band
Ability: Technician
or
-Bullet Punch
-U-turn/Knock Off/Superpower
-Defog
-Roost
Nature: Impish
EVs: 248 HP/252 Def/8 SDef
Item: Scizorite
Ability: Technican
Therian Tornadus:
-Hurricane/Air Slash
-Superpower/Focus Blast
-Knock Off
-U-turn
Nature: Naive/Timid
EVs: 4 Atk/252 SAtk/252 Spe (Naive) or 132 HP/160 SAtk/216 Spe (Timid)
Item: Life Orb (Naive)/Assault Vest (Timid)
Latias:
-Draco Meteor
-Psyshock/Thunderbolt
-Defog
-Healing Wish/Roost/Recover
Nature: Timid
EVs: 72 HP/184 SAtk/252 Spe
Item: Life Orb