Before some idiot comes in and mentions Cresselia, let me address this: almost every Uber has one or two reasonable counters. Deoxys-A simply cannot beat Scizor without massive prediction (which it cannot afford if it's up against anything remotely bulky to begin with), and Heatproof Brozong counters it consummately; however, the centralization caused by its very existence would be massive, and quite Latias like. Deoxys-A is quite capable of being checked by the likes of incredibly bulky Steel types, but every single one of them would be complete Magnezone fodder and your five remaining Pokemon have no means of stopping it.
I don't want to be harsh, but this is absolutely bullshit. You mention how Cresselia is a crap counter to Salamence and then you come up with something like that?? Heatproof Bronzong to counter Deoxys-A?? Seriously?? For your information, Bronzong is 2HKO'd by LO Thunder + Superpower most of the time. Let's just look at all the Ubers for counters:
Arceus: lol (He doesn't count at the moment anyway)
Darkrai: No counters, Ho-oh being the closest thing, but SR rapes it and not to mention Darkrai can just put her to sleep.
Deoxys/Deoxys-A: Not happening
Deoxys-D: Steels, but 1) No-one uses Deoxys-D and 2) Steels aren't going to stop it doing what it does (Entry hazards, Knock Off, etc).
Deoxys-S: Steels again, but nothing is stopping it get in at least 1 layer of hazards unless your name is Shaymin-S, Darkrai or Mewtwo wearing a Scarf. If you though Froslass was bad in UU, try Deoxys-S on for size.
Dialga: lol
Garchomp: Hard to counter, Timid Lugia and Cresselia probably being the closest thing to a counter.
Giratina: Defensive Pokemon, therefore it doesn't really need to be countered, although nothing is going to be killing it quickly either without boosts. CM Giratina is also a bitch.
Giratina-O: lol
Groudon: Fine. Lugia, Cresselia, Giratina are all reasonable counters
Ho-oh: Everything risks getting OHKO'd or 2HKO'd by this thing, anything that could beat it (Garchomp, Tyranitar) risks getting burned.
Kyogre: lol Quagsire, Ludicolo, Shedinja. Latias and Palkia can counter most sets, but isn't going going to be switching in more than once (A bit like Registeel is to Raikou)
Lati@s: Blissey, although if the Lati@s user decides to be funny and runs Refresh, Blissey loses too.
Lugia: See Giratina
Manaphy: Lati@s
Mew: Good luck.
Mewtwo: See Mew
Palkia: lol
Rayquaza: lol
Shaymin-S: SkarmBliss, albeit unreliable
Wobbuffet/Wynaut: lol
So 9 out of 24 Ubers have feasible, albeit unreliable counters, while the rest are flat-out uncounterable.
Back to the topic at hand, Cresselia is not a horrible check to Salamence either. RestTalk+CM Cresselia with Ice Beam is a real bitch. If Mence absolutely requires Scizor and Tyranitar to remove Cress, then you would question if his sweeping/supporting abilities actually need more support than an Uber does.