I don't think its defences and speed especially with all the new 100+ base pokemon will really cut it using a SD set. In theory Dragon Dance or maybe a late game Scarfer seem the best options to me.
CB Max Donphan can't even manage to OHKO Garchomp with Ice Shard, so no.maybe donphan would be able to take a hit and possibly KO it with ice shard.
same with mamoswine if you can catch him on his setup turn
Maybe it's because I don't play singles, just VGC, but I don't see what all the hype about OH! NO! NO! is about. I mean, he has an amazing sprite, but... :/ from a VGC perspective, there are just so many mons that outspeed and 1HKO him. Palkia (spacial Rend), Salamence (who neuters his Atk), Banded Flygon (lol), Garchomp (with a band or Orb), Scarfed Latios and Specs Latias. All of which were allowed in VGC '10 and quite possibly could be in VGC '11.
Is it different in singles?
Levitate Bronzong.
So he doesn't seem to get a Physical Fire move. At least the weird Grass / Steel land mine thing has a SMALL chance at killing it.. right? Skarmory can survive its hits decently as long as you aren't put in a bad place from Taunt. Its still not going to take hard hits well from scarfed things like Flygon or Garchomp (Garchomp can nearly OHKO even through a Haban Berry). CB Scizor hits it for 65% on average while CB Mamoswine Ice Shard has a good chance at wiping him out in one hit (after rocks). Scarf Latias or Salamence always OHKO him after Stealth Rocks. Jirachi always 2HKOs after rocks with Iron Head!
Onono Dragon is a massive broken obvious Uber threat - If we were still played 4th gen. Look at all the hard hitting Pokes who are much, much faster. Like that mole! Lots of other things have insane attack and speed, enough to break this dragon in one hit. Onono is attracting a lot of attention because he hits harder than Garchomp and has both Swords Dance and Dragon Dance. So what?
If people can drop the notion that everything must be walled you can see this thing is actually fairly easy to revenge kill (assuming Haban or Yache Berry hes still taking heavy hits with his average defenses) and isn't instant death to stall teams. Even modern stall can likely take him out with Gyarados + Forretress (Sand + Toxic Spikes) but don't forget some new 5th gen additions like the afore mentioned Grass / Steel land mine and old Skarmory / Forretress (admittedly not much else).
Its big and damn scary, but besides the hyper powered attack the rest of his stats aren't much worse than Salamence. 97 Speed really hurts him.
It runs in an entirely different field. It plays in OU like the other DD'ers/CB'ers/Scarfers. It'll have it's perks over mence, and chomp, and people continue to compare it to the others. Hype is one thing with people spewing "UBER UBER" all over the damn place, but tiers shouldn't even be a factor yet. Ono is about as overhyped as all the other pokes, but gets more flame then the rest because he can't compare to the other dragons? Then stop comparing it to the other dragons, open up your damn perspectives, and look outside of that! Does that make him overhyped? NO. Is Ono still a strong pokemon? YES.
What does it's SpA have to do with how good it can use DD/SD? Not really getting you're point there. In Mence's case, the SpA was important, so that it could get around stuff like Brozong and Skarmory with Fire Blast, and have a Draco Meteor to boot. However, just because SpA is important to Salamence even on its DD sets, that doesn't mean it is for the other dragons--which brings me to Garchomp.Uh, what? Why would be not compare Onono to Salamence and especially Garchomp, the most similar pokemon to it? It does not play on a "completely different field" to the other two, because they'll likely be fighting alongside each other in OU for a while in the beginning at least.
It's definitely outclassed as a DDer / SDer by Salamence and Garchomp respectively, because of it's inferior SpA and 'meh' movepool. This pokemon will be best as a Choice Bander (even Choice Scarf is suspect with Sazando and Flygon around)with Magnezone or Shanderra support, because of how hard it can hit and the fact that it can't take hits very well.
This dragon is da man! With Dragon Dance, he is going to hit HARDER than salamence. He can use SubSword Dance pretty damn well.147 base atk, he can destroy every pokemon when he gets a SD behind sub. Anyways, nice pokemon gamefreak, except its broken >_>