Couple things on BW.
Tyranitar being at 50% usage doesn't surprise me whatsoever as sand balanced and offense is quite easy to fallback on and it's not like using Tyranitar a ton makes you 'predictable' like it would for some other pokes as you can run a lot of things on sand, ofc. I used 4 Tyranitar in 4 games and have 0 regrets.
Keldeo not being in the top 10 in usage is crazy; this thing is still quite good..top 3 in the tier kinda good. EBelt is great in general while Scarf is nice to clean rain or offense and even CM fighting gem, specs, etc. can find its way onto teams. Not sure why it dropped to 13th in usage, but that's still 15% and there was a fairly small pool of games (like 60 of them), so I guess it's not too bad for the water pony.
Hydreigon is a fucking monster and the 75% win rate attests to that. This thing is so great at breaking balance and bulky cores right now while it doesn't have many drawbacks. I used it myself vs Jimmy Turtwig (won with it) and faced two of them (lost both to stone misses, which probably inflated its win rate quite a bit, but still Hydre is a boss rn). Glad to see it getting a fair shake in the current BW meta after not seeing as much use beforehand, but I could see it going into the top 15 quite easily.
Rain (Poli) sitting at a 67% win rate is sort of surprising as I personally make sure to prepare a ton for offensive waters and pack a flying resist, but I know some others fail to do so and there's a bit more to rain than hydro/hurricane spam, for sure, so it's not /that/ shocking. I guess it's also worth noting that rain was used 15% of the time, meaning only 9 matches, so this isn't too indicative of the playstyle as a whole and its consistency (or lack thereof) in the metagame.
Skarmory and Ferrothorn both sitting fairly high in usage doesn't surprise me at all given the emphasis on spikes in the current metagame and I think both of them saw a fair amount of use. With that said, Excadrill hasn't done much to up the spin game in the meta, so this isn't too surprising, but Starmie sitting up in the top 5 seems fair given the importance of hazards and controlling them rn (also, offensive star destroys a lot of common offense like the stuff smurf uses while fatte star is easy to slap on as a check to keld, spinner, etc.).
Reuniclus didn't see much use (Alakazam fits onto a lot of teams better right now and it's seeing 18% usage with a 45% win rate), but the 20% win rate probably stands out to quite a few people. I still think it's a great pokemon and I'm sure others do, but I hope some of the "omg reuni is ridiculous and ruining the bw meta" hype is dying down as it simply isn't too bad and it's reasonable to prepare for currently.
Slowking needs to see more usage in BW OU in general - this thing is godly and I'm sure Jirachee can attest to this.
Kyu-B only seeing 1 use is sort of surprising ngl, but Hydreigon has been stealing its thunder and the direction the metagame is heading in makes KyuB a bit less appealing.