This is the set I have been using for a while:
Kyurem-White @ Choice Specs
Trait: Turboblaze
Nature: Modest
EVs: 252 SpA/252 Spe/4SpD
-Draco Meteor
-Ice Beam
-Fusion Flare/Focus Blast
-Focus Blast/Earth Power/Flash Cannon
I haven't played ubers much but from what I've seen Kyurem-W is still effective despite the introduction of Xerneas and Fairy types in general. There are bad and good news about it:
The bad news:
-Draco Meteor can no longer OHKO Dialga on the Specs set, so it's forced to rely on Focus Blast for that. It also misses the OHKO against most Kyogre variants which is unfortunate. Hopefully it will get Freeze Dry...
-It no longer has perfect coverage in 3 moves so depending on its moveset there are pokemon who can reliably check it if it's locked into the wrong move with its Choice set (Most notably Azumarill and Assault Vest Tyranitar).
-While Xerneas takes ~80% from Specs Ice Beam, it will enjoy switching on Draco Meteor and use Kyu-W as setup bait. There are two ways to get around it though, which I'll mention later.
The good news:
-SR weakness was easily Kyurem-W's worst flaw in BW but now that entry hazards are much easier to deal with in ubers, especially when powerful and resilient pokemon such as Lugia and Arceus himself get Defog, Kyu-W is free to switch in much more often than before and wreck havoc.
-As I mentioned before Xerneas is a problem, but Kyu-W can actually OHKO it with Flash Cannon on the switch. FC however faces competition for a moveslot from Focus Blast, Fusion Flare and Earth Power (Ice and Dragon STABs are of course a must) so it's not easy to fit that in. Another way to get around Xerneas is to pair Kyurem-W with something that checks it. Aegislash resists everything Kyu-W is weak to and is a solid check for the rainbow deer. Other good partners that can check Xerneas are Arceus-Steel and Ho-oh, who can also check the less common Arceus-Fairy.
-Based on what I just said it's obvious that Kyu-W is a fantastic lure for Xerneas. Most players will try to keep it healthy for lategame sweeping because it's Geomancy set is a one time deal, but Xerneas is the only common pokemon in ubers that can stomach Kyurem-W's Draco Meteors: that's when you bring your Xerneas check in and either force its out or ruin its sweep.
Concluding, the Defog buff is the best thing to happen to Kyurem-W in XY, while the existance of fairies -especially Xerneas- is the worst. The Ice Beam nerf is practically unnoticeable from what I've seen, but Draco Meteor failing to OHKO Dialga and Kyogre is pretty annoying.
Kyurem-W's weakness to Xerneas can be turned into a strength by taking advantage of its ability to lure the Life pokemon early in the match and from there deal with it accordingly with team mates, which makes Kyu-W a better team player than it used to be in BW, where it was more of a mindless Draco Meteor spammer.
