Just so you know, Swift Swim and Drizzle are banned on the same team. Its either one or the other.
Double Team is also banned is competitive play.
Ferrothorn wants an entry hazard, preferably Stealth Rock over Toxic as you lack it currently and it ensures many KO's. Spikes are also an option over Gyro Ball and likewise Thunderwave over Leech Seed. Stealth Rock is the most important however. Sassy is also better than Careful to power up Gyro Ball (make sure you have 0 speed Ivs too). Rocky Helmet is a gimmick and i really wish people would stop using this. Ferrothorn wants Leftovers always or its durability is drastically cut short.
As for Politoed;
Politoed @ Chesto Berry
EVs 252 HP / 186 Def / 72 spDef
Bold Nature (+Def, - Atk)
Trait : Drizzle
- Perish Song
This is my favourite Politoed set at the moment. Scald and Hypnosis are there to cripple many things that stop him. Rest lets you heal and thus maintain your weather. Perish Song is nice to phaze things like BS SmashPassing teams which you currently have no defense against.
Toxicroak @ Life Orb / Leftovers
Evs: 244 HP / 252 Atk / 12 Def
Adamant Nature (+Atk, -SAtk)
Trait : Dry Skin
- Bulk Up
- Drain Punch
- Sucker Punch / Ice Punch / Stone Edge / Payback
This set lets you play defensively with Toxicroak. Bulk Up is awesome in the rain as it lets you heal and tank over many things. Drain Punch is for further healing and STAB. Substitute protects you from status and the like. The last slot is up to you. Sucker Punch is nice thanks to its priority and works nicely with Sub as that forces them to attack you basically. Ice Punch hits Gliscor, Stone Edge hits Gyarados and Payback is the most powerful option vs ghosts and psychics but is otherwise outclassed.
For your last few slots you should abuse things which benefit from the weather; Starmie, Tornados, Thundurus, Rotom-W, Virizion, Azumarril, Scizor are all fantastic choices. There are many more but its up to what you want those last few slots to do.