Staraptor is not seen in Ubers because it is too frail and gets worn off too quickly. It does not have the time to Roost the damage off, so it will be easily weakened and taken down. Moreover, Giratina is super common in Ubers, and it tanks Staraptor quite well. Adamant, Choice Banded Brave Bird only tops at 45.52% to a 248/252+ Giratina, allowing it to burn it, phaze it, and Rest the damage it has lost. Ho-Oh, despite its glaring Stealth Rock weakness, completely outclasses it. Its Fire STAB, which also has a good rate of burning the opponent, makes it a better option over Staraptor, which has to rely on another recoil move to hit the hardest. In addition, Ho-Oh's enormous 106/154 bulk allows it to Roost on plenty of Ubers's moves, as most of them are special.
As of Flying Arceus... Drop Swords Dance. It's not in the Other Options for nothing (I completed the analysis so I know :P). You are wasting so much potential by giving it Swords Dance instead of Calm Mind. Flying is a great attacking STAB only resisted by 3 types out of 17. Flying Arceus with Refresh/Recover/Calm Mind/Judgment is a phenomenal stallbreaker and wallbreaker. You get to set up on Snatch-less Chansey (and Blissey), and then wreck things apart. Be cautious of Zekrom though, as it can tank a +4 Judgment with ease, and shred Arceus with a single Bolt Strike. Like any other sweeper Flying Arceus appreciates entry hazards which allow it to sweep better, and it could also enjoy Rapid Spin support due to its weakness to Stealth Rock.
As I presented, Flying Arceus is more than viable, just not Swords Dance; although Shaymin-S is a great sweeper too. With SubSeed, it can easily set up on Blissey and Chansey, Leech Seed them, and FlinchHax to death. Thanks to its high base Speed, it would be perfect for an Heavy Offense team; pair it with a fast Spikes user, such as Deoxys-S or Deoxys-A, and Shaymin will have a field run because of the switches it forces. Deoxys-A/S can also prevent Stealth Rock on your hazard by Taunt and high offenses, respectively. Shaymin-S does not care about the weather it's used in, as it is not weather dependant: it's ability is not Chlorophyll and it doesn't use SolarBeam or Thunder. Rain would be the preferred one in my opinion, as it nullifies its Fire-weakness, though sun or sand would work just as well.