Politoed
Rest-talk is a preference of mine, but if you're running those moves, I would go with a more speed based EV spread -- 196 HP / 60 SP ATK / 252 SPD --
Shedinja
Give it 4 HP EVs that will do absolutely nothing, just to say you did it :P
In all honesty, no major changes needed.
Raikou
Choice Scarf or Life orb for the item. He needs the extra power and speed, to be honest. But when you're running the event moves that lock you into Rash, a choice scarf will help make up for the lost speed of the glorious timid nature he needs...
Or you can just hit like a truck and give it Life Orb.
Swanna
I prefer Life orb, but Specs will work well enough.
If you run Life orb, drop HP Ground for Roost.
And no matter what you do, drop Scald for Surf.
Parasext
Spore > Brick Break. Put them to sleep to give extra set up time.
Ferrothorn
You could use a good spinner, and he isn't doing a lot of support for your team. So with that in mind, I recommend Tentacruel.
Tentacruel (M) @ Black Sludge
Trait: Rain Dish
EVs: 252 HP / 4 Def / 252 SAtk
Modest Nature (+SAtk, -Atk)
- Toxic Spikes
- Rapid Spin
- Acid Spray
- Scald
Make sure you're switching into a special attacker when you pull him out, just a heads up.
Toxic Spikes sets up hazards that will help finish off pokemon and get passive damage going. These are recommended to be late game hazards though, so you don't get in the way of Hypnosis and Spore.
Scald is for STAB and hitting steel types, poison types, flying types, and levitate abusers. Acid Spray is STAB and helps make you hit harder.