OK, I said I would answer, and here is my answer.
Kyogre: There's a problem with having him as your lead. Let me explain why. There are many common leads, but Deoxys-S appears almost half of the time. And if he appears, you're probably screwed. Here's the scenario. Deoxys-S comes out! You attack with a move, probably Hydro Pump. Deoxys-S hangs on and sets up Spikes/SR. Now, Deoxys-S can switch into something to take your Hydro Pump, and you'll hit pretty hard with Choice Specs, but not hard enough. You gotta switch, right? And since those hazards are up, you wanna spin them away before they come back. So, you switch to Forretress. However, Forretress's Sturdy isn't active b/c it gets hurt by hazards. Then, it can get OHKOd. This scenario can be altered, but the point is, Forretress has to stay at full HP so it can survive with sturdy. Make it your lead so it can't be hurt with hazards. Otherwise, nice Kyogre. Although, without Scarf, no Water Spout. Use either Signal Beam, or HP Fighting.
Palkia: Use Hydro Pump over Surf.
Forretress: Am I really supposed to try and improve this? Everyone uses this Forretress. Well, maybe even out the EVs a bit between defenses. Besides, Flamethrowers will be weakened in the rain.
Arceus-Steel: I'll be honest with you. This guy stinks. Judgement won't be hitting very hard, and it'll get taken out quickly. Besides, you already have two special attackers. Use a different Arceus set. Physical. I have two sets for you, one if you want Steel, one if you are flexible.
Arceus-Steel @ Iron Plate
Nature: Jolly
EVs: 252 Atk, 252 Spd, 4 HP
Moves: Swords Dance, Recover, Iron Head, Earthquake
What I love about Arceus is its natural bulk. It can take a hit or two easily while setting up, unlike other sweepers. This set is a bit like Garchomp's, but works well with Arceus's godlike stats.
OR...
Arceus-Ghost @ Spooky Plate
Nature: Hasty
EVs: 188 Atk, 68 Sp. Atk, 252 Spd
Moves: Shadow Force, ExtremeSpeed, Earthquake, Recover
This works better IMO because of better typing on its part. Not many Pokemon can counter its powerful moves, and it also beats ExtremeKiller easily. Almost no Pokemon resist Shadow Force, so there's nothing to switch into.
Lugia: Factoring in the large amount of Thunder/other rain teams, plus Lugia's 4x weakness, plus low Sp. Defense Evs...I would run Calm Mind instead of Whirlwind. You could replace another move; Lugia just has so many options... Let me provide damage calcs.
Timid 252 Mewtwo vs your Lugia: 58.2% - 68.8%
Scarf Modest 252 Palkia vs your Lugia: 48.1% - 56.7%
So, considering they outspeed you, you're dead; unless you Roost first turn. Then, half damage, but with a crit, and considering hax... run Calm Mind.
Garchomp: As trachy said, probably want to run Adamant Choice Scarf Outrage. So no Swords Dance. Replace it for Crunch.
