Got the deviation low enough for reqs yesterday and figured I’d chime in to agree with dragonuser/doom/others. Kyurem-B clearly won’t be single-handedly sweeping through teams, but that isn’t the only justification for a ban. Virtually everything we’ve voted out of the tier can be checked, but the impact a pokemon has on both team building and battling is much broader than some posts in this thread seem to imply. Even though the detrimental effects might not be readily apparent in every match, closer inspection has led me to believe Kyurem-B’s presence actually does adversely affect our tier.
After some thought, I think Kyurem-B’s most grievous offense is the enormous restriction it places on team building. It may not be considered “fast” by the current metagame’s standards, but its unrivaled power and efficient coverage immediately make the inclusion of almost anything slower a liability in team construction. Ferrothorn, Forretress, Breloom, and Scizor are exceptions to this, but the first three checks lack reliable recovery, and Breloom can’t switch into Kyurem-B directly like the others. Players can theoretically avoid giving Kyurem-B a chance to fire off one of its obscenely powerful moves by packing multiple pokemon capable of outspeeding and OHKOing this behemoth, but this strategy is difficult to implement because of Kyurem-B’s oft-underestimated bulk. Assuming Kyurem-B doesn't have some (debatably more distressing) investment in bulk, Garchomp, Salamence, Terrakion, specs Keldeo, offensive Latios(as), Landorus, and Thundurus-T are the only things in the tier actually capable of doing this “reliably” (in quotes because the first two are forced to Outrage, while the last two have to rely on Focus Blast’s awful accuracy). We can factor Jirachi, another respectable check, into the equation, but we still aren’t left with much to choose from. Even disregarding this extremely small pool of viable options, nearly all of the vulnerable offensive checks are utterly ruined by scarf sets, and the few defensive checks are severely crippled by mixed variants. While other pokemon in the tier can certainly trip up common checks with alternative sets, Kyurem-B’s towering attack stat affixes far graver consequences to this guessing game. As a result, players keen on surviving all forms of Kyurem-B’s onslaught are often forced to fill already limited team slots with more than one pokemon off this brief list (a team building cap that, I'd argue alongside dragonuser, cuts down on the number of usable team archetypes).
While I highly doubt Kyurem-B is solely responsible for the metagame’s staleness, I do believe its existence is a contributing factor. Accordingly, I’ll be voting it out; I encourage others to consider doing the same. Like some previous posters, I agree that OU has some arguably bigger concerns (Genesect, Deoxys-D, Tornadus-T, etc.) at the moment, but I wholly reject the idea of keeping something problematic inside the tier simply because there are other, more problematic things surrounding it. Regardless of a problem’s relative size, if we’re given the opportunity to fix one, we should take that step towards betterment until we’re allowed to cast ballots on the even-more-monstrous remainder. At their most fundamental level, suspect tests are meant to improve the metagame—others are obviously free to disagree with my rationale, but I'm ready to start making that happen.
edit: yep, all threats restrict team building--the operative word in my sentence was "enormous"