I've been liking the UU metagame this round, which is suprising considering I've never been much of a stall person, but its been fun to play. I find Haze Milotic to be an incredible pokemon overall as it checks DD Kingdra very well, as well as a lot of other boosters, including BU Gallade which has been used recently to break through other stall teams. It also ruins Venomoth and Gorebyss attempts at Baton Passing.
Chansey is another obvious choice. It is nearly impossible to OHKO, let alone 2HKO. It turns most special attackers including SF Nidoking into complete jokes. It can support its team easily with Wish support or Aromatherapy support, while spreading status at the same time. Aside from being unable to take certain physical attacks and the lack of resistances, there isn't much reason not to use Chansey.
Roserade has also proven to be a very reliable Spiker, due to its Speed, special bulk, and it can use Giga Drain, Leech Seed, or Rest + Natural Cure to stick around longer than other Spikers like Qwilfish and Froslass. So far my team has had problems with Roserade more than anything else, but i've still been able to deal with it.
If anything is broken, I'd say it would be Chansey. It simply walls too much of the metagame, and few things can safely switch in without getting crippled by Toxic or T-Wave.