Update Time
A ---> A-
A ---> A-
A ---> A-
A ---> A-
A- ---> B+
B+ ---> A-
B+ ---> A-
B ---> B+
C+ ---> B-
C+ ---> C
Some of these updates might come as a bit of a surprise while others shouldn't. Manaphy has fallen off quite a bit recently with people now prepared for its Z Rain Dance set, as well as facing stiff competition as an offensive Water-type in general from both Greninjas. Rotom-W has lost some traction as well, due to the fact that it is no longer needed on 50% of teams with Talonflame no longer in the tier, and with the introduction of Z moves, Pokemon such as Landorus-T, Heatran, and Garchomp have a much easier time breaking through it. The burn nerf hurts it quite a bit as well, because now stuff like Latios and Mega Venusaur don't mind the burn nearly as much, and are more consistent at checking it. Buzzwole is still great for checking many physical threats in the tier, but with offensive Landorus-T being so common, SD Bulu, as well as special variants of Pheromosa emerging, it's not a very consistent check to a few important Pokemon it was intended to check, and it doesn't seem right to keep it in the same rank as Ferrothorn, an OU standard. Mega Venusaur I know is one a lot of people will disagree with but the biggest issue Mega Venusaur has is that outside of more offensive presence and Thick Fat, it really doesn't offer that much more to teams than Amoonguss, which doesn't take up a Mega slot. Overall, Mega Venusaur is better in general, but if you take it being a Mega into account, relying heavily on a low PP move for recovery, and no Lefties, it's not nearly as consistent at dealing with some of the Pokemon that Amoonguss checks, such as Tapu Koko, Ash Greninja, and Tapu Fini, which heavily punishes Venusaur with Natures Madness. Mega Venusaur is better fit for more BO builds, but at the same time, Amoonguss offers very similar role compression, but giving you the ability to use something else like say, Mega Metagross because why wouldn't you use that.
Zygarde 10% shouldn't be too surprising. At the moment, it is being heavily overshadowed by its counterpart, and even with CB, it sort of has Pheromosa syndrome, where if it can't kill something, it's probably going to die. However unlike Pheromosa, Zydog is not THAT strong, and fails to OHKO a good portion of the meta. It's also very susceptible to being revenged by most common Scarfers, Koko, Greninja, and being walled by Bulu sucks. In fact, even CB Zygarde 50% has shown itself as accomplishing similar results, but with added bulk instead of Speed, which is arguably just as useful, and lets it spam Thousand Arrows more comfortably. Mence and Volcarona are both Pokemon that have seen a lot of usage in the last few weeks, and even already in SPL. Both of them have the capabilities to rip through teams with their respective Z moves, and with people relying on Scarf Lele as their revenge killer, they take full advantage of that. When played correctly, so many common builds right now just completely lose to both of these mons, and they are easily one of the most terrifying sweepers in the tier. Scolipede just recently got some massive hype in the form of an offensive SD set that punishes the heavy use of all the Fairies, Grasses, and Ground-types running around. Its typing lets it set up on the likes of Tapu Fini, Bulu, Ferrothorn, Mega Venusaur, and defensive Landorus-T (Stone Edge can't OHKO), and proceed to tear apart bulky and offensive builds thanks to its Speed boost ability and good coverage. A +2 Hydro Vortex can OHKO most of the bulky grounds found in the tier, as well as dealing very solid damage to Celesteela. It's not very easy to revenge either, and its coverage makes it hard to wall defensively as well. Mamoswine got a rise because it didn't fit with most of the trash Pokemon in C+, and it can still run a very strong offensive SR set as well as checking Koko, which is always great. Xurkitree is bad and super niche outside of Webs.
Also if there are any posts that complain about A- being inflated then expect it to be deleted, we are well aware. There is nothing wrong with a rank being inflated if it's accurate, and we are not going to move things around for the sake of it. It just shows that there are plenty of good picks in OU, but none of them are necessarily top tier.