Garchomp isn't sweeping, and if it is sweeping, it's a sure sign you're playing badly. Garchomp certainly shouldn't be considered Uber under the Offensive characteric, as if you pack the right Pokemon you shouldn't really be losing more than one Pokemon per match to a sweeper Garchomp. Garchomp's real strength is as a revenge killer.
I agree. I haven't seen Garchomp perform that well in the sweeper role, personally, and certainly not at the extent at which it breaks the offensive characteristic. Personally I think Garchomp appears to slot in very nicely into the OU metagame; it's the sort of check for Steel-types that I've been missing, and it can function as a sweeper, revenge-killer or lead, none of which are too difficult to handle, but then I never thought it was Uber originally. Naturally it's being used most, I assume due to a combination of notoriety, nostalgia and SEXP, but I don't think that anybody is still arguing that that is indicative of Uber status. In short, Garchomp is, from my experience, pretty predictable, vaguely interesting to face and undoubtedly top-tier. But Uber? I doubt it. If it comes down to nothing else, I honestly far prefer this metagame to the current Standard play.
Manaphy... I don't really know where to put it. It's been underwhelming on my team and certainly quite awkward to deal with at times by reasonably good opponents. Not as long-lasting as it seemed during the secluded test, but I feel still a tricky customer. Not Uber, just something I have trouble with. Hmm...
Latias: No comment.
Today, every single team with Garchomp has Magnezone with it. Most of those teams also carry Brongzong, who happens to be about the one thing which can stop Garchomp 100% of the time. 3 slots per team centralised around Garchomp.
So... like most teams with sweeper Scyther in UU carry a rapid spinner, a stealth rocker and something to take its weaknesses? I don't see your point.
Garchomp, as you probobly summaried from the 'Zone to help Chomp, Sandstream, Chomp, and Bronzong to best Chomp on every team' thing before, is Uber. It's in a whole other class to Manaphy and Latias. Usually, when a pokemon fares well in Ubers, especially when it's weak to a common attacking type there (x4 to Ice, x2 to Dragon), and it's stats are not as large as other Ubers, yet it is still highly used and sucessful, that's usually a sign of being Uber. When it's sweeping in a OU-like metagame prepared for it, that's a sign of Uberness.
Scizor, Tyranitar and Forretress perform well in Ubers, as do a number of Pokemon in OU. There's also Lucario. And, if it weren't for Rayquaza, Salamence would probably be added to that list. Plenty of Pokemon do well in Uber and aren't strong enough to break OU. Second point, Garchomp isn't really sweeping, not if you don't count running a scarf and killing two weakened Pokemon at the end of a game as 'sweeping', nor locking itself into Outrage and getting itself revenge-killed. Perhaps, overall, it's better than Latias or Manaphy. But all three do completely different things, which is why nobody can compare Lucario and Salamence as individual Pokemon.