However, one cannot have both an Arceus-Steel and an Arceus-Rock in the same team, and Tyranitar is also a very undesirable Pokémon to have in many Über teams, since many of them attempt to abuse either the rain or the Sun provided by Kyogre or Groudon respectively, and the Armor Pokémon's Ability conflicts with that. And since the only other commonly-used Pokémon in Übers that resists both Brave Bird and Sacred Fire is Zekrom, which strongly dislikes being burned by the latter, I believe that it is generally much better for Arceus-Steel to have an attack that can KO Ho-Oh, rather than putting something else in the team specifically to resist both of Ho-Oh's Same Type Attack Bonus moves (and from my experience, most teams, especially those that are generally more offense-oriented, could hardly afford to have a spot taken up just for that purpose anyway).
Also, it is true that Choice Scarf Ho-Oh in the Sun would destroy this Arceus-Steel before it gets the chance to fire a Stone Edge. But not only are such Ho-Oh rather uncommon, but they are also not that threatening overall in my opinion, due to their lack of Life Orb, Recover and moves like Substitute and Flame Charge, and also the fact that Choice Scarf locks them into one attack. If you fear Arceus-Steel being taken out by such a Ho-Oh, then you could simply switch it out the first time you see the Rainbow Pokémon, and then observe whether or not the opponent's Ho-Oh recovers any health from Leftovers or loses any health from Life Orb, and then battle accordingly. If the opponent's Ho-Oh does turn out to not have Choice Scarf, Arceus-Steel can then crush it with Stone Edge the next time Ho-Oh appears before it.
In any case, if this helps in your testing, below is "Divine Lightning", the team in which my Arceus-Steel was specifically designed to be used. It peaked at #4 on the DW Ubers ladder on the Pokémon Online server with 1607 points, and is probably my third most successful Über team ever. Since I am currently taking a break from laddering until the release of Pokémon Black 2 and White 2 (at which point the metagame would probably look very different anyway, making the teams that I currently use most likely irrelevant in it), I guess there would be no harm in revealing my team here:
Lucifer (Thundurus) (M) @ Focus Sash
Trait: Prankster
EVs: 4 HP / 252 SAtk / 252 Spd
Modest Nature (+SAtk, -Atk)
- Focus Blast
- Taunt
- Thunder Wave
- Thunderbolt
Uriel (Latios) (M) @ Soul Dew
Trait: Levitate
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature (+Spd, -Atk)
- Draco Meteor
- Psyshock
- Surf
- Thunder
Raphael (Kyogre) @ Choice Scarf
Trait: Drizzle
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature (+Spd, -Atk)
- Ice Beam
- Surf
- Thunder
- Water Spout
Gabriel (Palkia) @ Leftovers
Trait: Pressure
EVs: 4 Atk / 252 SAtk / 252 Spd
Naive Nature (+Spd, -SDef)
- Focus Punch
- Spacial Rend
- Substitute
- Thunder
Michael (Dialga) @ Life Orb
Trait: Pressure
EVs: 4 HP / 252 SAtk / 252 SDef
Modest Nature (+SAtk, -Atk)
- Aura Sphere
- Draco Meteor
- Stealth Rock
- Thunder
Yahweh (Arceus-Steel) @ Iron Plate
Trait: Multitype
EVs: 252 HP / 4 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Recover
- Roar
- Stone Edge
- Will-O-Wisp