Ubers! :D
First off, your team has a lot of problems, mainly that your whole team is quite slow. Palkia can still get outsped by other Scarfers, and I can see your team getting swept by something like a Scarfed Kyurem-B with Outrage, or a DD Salamence with Moxie. You focus too much on boosted sweeping, and don't have any reliable special attackers that won't get hit hard. Both Kyurem-W and Reshiram are frail, and can get pulverized. Arceus is the only one who I see surviving, but he's the XtremeKiller.
Groudon
I would go for a more defensive set, to give you the time to set up SR, speaking of, which almost half of your team is weak to. Later on you're gonna need to replace some Pokemon to tone down the SR Weakness. But I suggest this set...
Groudon @ Leftovers
Nature: Impish
Trait: Drought
EVs: 252 Hp/4 Atk/252 Def
Moves:
- Stealth Rock
- Dragon Tail
- Earthquake
- Stone Edge
Works better. You already have Arceus for a Dancer anyhow.
Kyruem-W
Use Expert Belt over LO, it will be more reliable.
Reshiram
Sorry, has gotta go. Just is way too repetitive after Kyurem-W, and will get swept just as easily as its big brother. Don't worry, I'll keep the Tailwind support.
Ho-Oh @ Life Orb
Nature: Adamant/Jolly
Trait: Regenerator
EVs: 252 Atk, 252 Spd, 4 Def
Moves:
- Tailwind
- Sacred Fire
- Brave Bird
- Roost/Recover
I always thought this guy was underestimated. Huge SDef in a tier where half is special... plus such powerful stats and a 50% burn chance in Sacred Fire, plus Regenerator... WOW. Anyhow, this set is self-explanatory. However, the toss-up between Roost and Recover lies in the Ground weakness without the Flying type. However, I would go with Roost anyway.
:
Arceus
Use Lum Berry, and Recover over Brick Break.
Palkia
Nice, no suggestions apart from trying a Timid nature to outspeed other Scarfers.
:
Ferrothorn
I love him. I really do. But if I were you, I think your team needs a spinner. That's...
Use the usual set, Impish nature, Lefties, Sturdy, T-Spikes, Spikes, Volt Switch, Rapid Spin. I'm too lazy to write it out. But don't get mad 'cause of the 4x weakness, Kyogre appears frequently AND that woulda happened with Ferro too.
Anyhow, hope I helped! :D