I see the quote in your sig still holds up.
Tier council decides, not staff
Unhealthy for the tier
Checking usage statistics and watching replays of officials
Uber (too powerful for OU), OU (Over Used, most used pokemon), UU (Under Used, less used pokemon), NU (Never Used, least used pokemon). Legendaries cannot be kept right now, but are banned still because of their power. Anything in Uber is banned from OU, UU and NU.