The arguments made for Garchomp moving into the Uber tier are (I really hate to say it) reasonable. I'd have to guess it's the extra 2 points in speed and the way Garchomp doesn't stumble on today's common hazards that are just enough to tip it over the threshold of OU. Such a pity, too, as having to counter it isn't that big a problem anyway.
Having something to counter the various dragons is not a problem, that is true. Every team should be able to do something against them. But when you need to have a counter for one specific Pokemon, it's overcentralization.
A number of (more experienced than I) team builders that I've seen post (not on here, as I didn't really read the RMT threads before Chomp's uber status) explained that their teams, in an OU environment, generally need 2-3 Pokes to counter Chomp.
Chomp is on it's own tier, being all but immune from paralysis (I think Tri Attack could do it), it's great base stats, only one weakness (which is reduced for one turn due to the berry), and then it's ability which can even keep it from being revenge killed. And unfortunately, the only steel type that can really do anything is Heatran or Metagross, who are both weak to Earthquake. Bronzong can stall around for a while, but can't really bring it down by itself.
Wait a second. Doesn't every team have to have a way to counter Gengar? Or Jirachi? Or Salamence? Or Blissey? Or Lucario? I don't think 'team restriction' is a really big factor with Garchomp...
I don't know if team's will necessarily become more diverse, but from some brief readings of the Smogon boards, I've seen more rise in stuff like offensive Starmie and Heatran. I'd say there'll be some shifts in the team, but probably move sets will happen that weren't too viable with Chomp.
As for the coutners of those OU Pokes: Yes, but your team doesn't have to have a specific counter for any of them. Blissey is completely crippled by any STAB physical attack, and probably OHKO if it's boosted. Salamence has already been pretty well covered, but can you honestly think of many teams who don't have an option to status a Poke? Gengar and Jirachi both share Ghost weakness, and Lucario and Gengar share a psychic weakness. Lucario is weak to...well, a lot, including the very common fighting. So while you do need counters for them, you don't need specific ones, and they can be applied to other Pokes.
I'm sure you've read the two Chomp threads in the 4th gen sub-forums. There were some viable counters posted. The problem with those counters was their only purpose was to take down Chomp. They were either useless otherwise or would be dead by the time their job was done.
And apparently, all the Pokes that were carrying HP Ice are now switching to other x4 weaknesses, such as HP ground and HP grass.
We're not going to see a down-flux of Ice-type moves without Garchomp, though perhaps less Bronzongs around.
I think we might see Pokes ditching some HP and Ice Fangs for other moves, since Chomp won't be a threat any more. Aerodactyl, for example, can use his STAB Rock attack for Salamence, Dragonite, and all the flyers.
lol thats a lot of words on pokemon.
If not, then play on the main server or, *gasp* fire up Wi-Fi on your DS. It's not that hard. The tier system isn't hard and fast unless you have a way of making it such. Until NoA makes Garchomp illegal to use over Wi-Fi... there's no reason getting up in arms about the ban to übers.
As I said, if you're a competitive battler, you probably understand the move to uber. Even then, you can (specify) differences in a standard rules match that you want/don't want to follow (or even, I know this is weird, play in ubers. It's quite a...unique experience). And if you're only playing for fun, it won't affect you at all.
NoA will never have a tier list. There is a banned tier in the Battle Tower, and the official Pokemon tournaments, but that's about it.