Well, I don't have enough info here to give you a full rate but I can say that your EVs and items need a TON of work. I won't suggest replacing Pokes unless ABSOLUTELY necessary though. And seeing as I'm at school, I can't really go into detail on the descriptions but I can fix those when I get home if needed.
First off, you should be leading Politoed if Rain is your primary focus. Second, use Toxic over Hypnosis. Hypnosis has atrocious accuracy. As far as the rest goes, I can't tell what you're trying to do with Politoed. Is it offensive or defensive? If it's offensive,
Politoed @ Choice Scarf / Specs
Timid / Modest Nature
EVs: 4 HP / 252 SpA / 252 Spe
- Hydro Pump
- Focus Blast
- Ice Beam
- Hidden Power Grass
If it's defensive,
Politoed @ Leftovers
EVs: 252 HP / 252 Def / 4 Spe
- Ice Beam
When I play Rain, it's one of these Politoeds, usually a ScarfToed. But your team, your choices.
Rotom-W: This is a standard Choice Rotom, use Scarf with it.
Ludicolo in OU on a Drizzle team should use SubSeed, which I don't find terribly effective but again, your team, your choices. Whatever you do with it though, it needs a new EV spread. If you're going offensive (NEEDS Swift Swim to be effective and as such can't really be used here), go with 252/252. Otherwise, SubSeed Ludicolo:
Ludicolo @ Leftovers
Trait: Rain Dish
EVs: 252 HP / 216 Def / 40 SpD
- Leech Seed
- Giga Drain
It pretty much does the same thing as every SubSeeder ever, only with Rain Dish support. Drop a Sub and Leech Seed, Poison for extra damage and Giga Drain for recovery and so you aren't Taunt bait.
Toxicroak: Pretty good, but Substitute and Focus Punch over Fake Out and Protect/Taunt. There are other viable options of course but SubPunch is what I'm most familiar with so it's what I'm suggesting here.
Ferrothorn: Needs Leftovers. No questions asked. And the EVs... I'm just going to write the set below:
Ferrothorn @ Leftovers
Trait: Iron Barbs
Impish Nature (Relaxed if using Gyro Ball)
EVs: 252 HP / 88 Def / 168 SpD (0 Spe IVs if using Gyro Ball)
- Stealth Rock
- Power Whip / Gyro Ball
- Leech Seed
Pretty standard Hazard setter here, drop Rocks, drop Spikes, Seed 'em and go from there. I prefer Power Whip for many reasons, better coverage, stable power, etc. Leftovers is essential for recovery.
Dragonite: Again, needs a bit of work. First off, Haban Berry is bad for Dragonite. It doesn't need a Berry with Multiscale, except possibly a Lum Berry for Outrage. It has better options though, like Choice Band and Life Orb. I'd imagine this is offensive, and so here's a Mixed attacking set that retains the Rain abuse:
Dragonite @ Life Orb
EVs: 76 Atk / 252 SpA / 180 Spe
- Aqua Tail
- Extremespeed / Earthquake / Roost
Hurricane is your main move, with Aqua Tail hammering a lot of what resists it and getting pseudo-STAB in the rain. Thunder wrecks Skarmory, Tornadus-T, and Tentacruel, among others. All 3 check Rain teams very well, so this is really nice. The last slot, all 3 have their merits which is why I've listed them all. Extremespeed revenge kills, Earthquake handles things like Jirachi and Roost heals off LO recoil and potentially resets Multiscale.
"Whether Castform the Weather Pokemon can weather the weather is dependent on whether the weather that it's weathering is the proper weather for it to weather. Whether the opponent can weather the weather is also subject to whether the weather that it's weathering is the right weather to weather. Whether Castform can weather the opponent is once again dictated by the weather and whether that weather is the favorable weather for weathering. But most importantly, you should know whether there will be weather to weather rather than what weather they will be weathering and whether they can weather that weather."
- Smogon's Castform analysis