rhydonphilip, if you'd like I
can give you reasoning for everything that was deranked. And while I'm making this post, I might as well add that the decision to put heavy emphasis on tournament finishes and cut down heavily on the list of Pokemon in the viability rankings (for now at least) received unanimous official support.
Honestly, since I deranked so many and because most of the deranks should be relatively obvious, let me cover the example you yourself brought up; Kyurem-W. Kyurem-W has some pretty awesome stats and it's typing is kind of cool, but it runs into a bunch of issues right off the bat. First is simple opurtunity cost; the second you run Kyurem-W that means you're either sacrificing a Primal, Xerneas, or another Restricted Legend that could fit your team better. Kyurem-W is rather ungainly as a Pokemon so odds are that it won't ever fit into the 'Restricted Legend that fits your team best' but I'll ignore that (and I'll also ignore the fact that a team that is a perfect fit for Kyurem-W is probably less than optimal overall).
Now before we go further, I should mention that I love Kyurem-W and I have tried (and failed) to use it well multiple times. The set that I honestly find interesting is the Specs variant, so we'll start by looking at that.
252 SpA Choice Specs Turboblaze Kyurem-W Draco Meteor vs. 252 HP / 4 SpD Primal Groudon: 220-259 (106.2 - 125.1%) -- guaranteed OHKO
Now, I've gotta admit that's really tempting stuff. Still, that calc is where all of the problems start. Sure, Draco Meteor gets the OHKO but on the flip side it's Draco Meteor. 90% accuracy is infamous for missing when you need it to hit most, and minimizing RNG factors when at all possible (do remember, a hypothetical Xerneas here never misses it's Moonblasts that OHKO basically everything after Geomancy). Still, there's hope! You do have a 100% accurate option to OHKO Primal Groudon.
252 SpA Choice Specs Turboblaze Kyurem-W Earth Power vs. 252 HP / 4 SpD Primal Groudon: 204-240 (98.5 - 115.9%) -- 87.5% chance to OHKO
A few problems here too though. The first is the fact that while it is 100% accurate it's not a 100% OHKO on 252 HP Primal Groudon, and if you look at the 252 HP/156 SpD set (which some players run to always survive Earth Power from opposing Primal Groudon) you get this calc:
252 SpA Choice Specs Turboblaze Kyurem-W Earth Power vs. 252 HP / 156 SpD Primal Groudon: 174-206 (84 - 99.5%) -- guaranteed 2HKO
Suddenly you have no chance to OHKO them. That's. . . not good. Well, how about Modest? So far all of my calcs have been assuming Timid. Once again, we have another problem. The second you opt to run a non Modest Kyurem-W, suddenly Primal Groudon and Primal Kyogre and all the other base 90s can outspeed you. That's really, really bad. I mean sure, you could run it on a team with speed control but Choice locked Pokemon aren't all that dependable on speed control teams because they rely on the speed control to function which means they can't be effective leads and if your Tailwind or TR runs out before they come in for the late game your in just as bad of a position. Still, that's Specs. What about Life Orb sets?
Well, and this should be no real surprise, if you run Modest Life Orb Kyurem-W you lose a decent bit of power over the Specs set, and Timid Life Orb loses even more power (don't even get me started on Modest Scarf).
252+ SpA Life Orb Turboblaze Kyurem-W Earth Power vs. 252 HP / 156 SpD Primal Groudon: 166-198 (80.1 - 95.6%) -- guaranteed 2HKO
252 SpA Life Orb Turboblaze Kyurem-W Earth Power vs. 252 HP / 0 SpD Primal Groudon: 177-211 (85.5 - 101.9%) -- 12.5% chance to OHKO
Please note that while the first calc is against the 156 SpD set, the second calc is simply against plain 252 HP Primal Groudon. 12.5% is pretty bad, and by pretty bad I mean terrible. So, let's assume that you want to run Modest and you're okay just assuming that you'll always get the OHKO on Primal Groudon which you won't. Even then, you need speed control in order to function well, and if you're using setup + restricted and that restricted isn't Xerneas then there's something of an issue. Now, thus far everything I've spoken about has been against Primal Groudon and really, you would beat it most of the time.
My point is that even with things you're supposed to beat, there are a disturbing number of cases were it'll be able to fire off an attack or two.
Now, let's take a moment to appreciate everything that destroys Kyurem-W.
252 Atk Parental Bond Mega Kangaskhan Low Kick (120 BP) vs. 4 HP / 0 Def Kyurem-W: 220-260 (109.4 - 129.3%) -- guaranteed OHKO
252 SpA Fairy Aura Xerneas Moonblast vs. 4 HP / 0 SpD Kyurem-W: 218-260 (108.4 - 129.3%) -- guaranteed OHKO
252+ Atk Huge Power Mega Mawile Iron Head vs. 4 HP / 0 Def Kyurem-W: 284-336 (141.2 - 167.1%) -- guaranteed OHKO
252 Atk Life Orb Mega Rayquaza Dragon Ascent vs. 4 HP / 0 Def Kyurem-W: 187-220 (93 - 109.4%) -- 50% chance to OHKO (50% is just too much, unless you want to run bulk, which is a bad idea because it cuts into offense and or speed which you can't afford to lose)
252+ Atk Ferrothorn Gyro Ball (111 BP) vs. 4 HP / 0 Def Kyurem-W: 186-218 (92.5 - 108.4%) -- 43.8% chance to OHKO
But wait, you say, I outspeed and OHKO Mega-Mawile with Earth Power. And I say, yes, yes you do. Unless of course they have speed control on their team like literally every Mega-Mawile team does. Then they set up their speed control and destroy you. How about the Ferro calc then? Who runs 252 Brave Ferro? Yeah, I agree, but once again I'm making a point.
That point is this: in addition to struggling to get the OHKOs that you'd be running it for, Kyurem-W has this bad tendency to be OHKO fodder itself. It doesn't matter if the chance is low, when dealing with anything exceeding a 7% chance players need to assume it's going to happen 100% of the time (we're now verging somewhat into personal opinion here). Simply put, expect the worst and plan for the best. And hovering above this all you have the fact you're using a Restricted Legend slot.
In conclusion, Kyurem-W probably will see some (quite limited) success this year and eventually be added somewhere lower on the rankings, but considering all of it's flaws and general lack of usage I really can't keep it in the Rankings in good conscious.