Mega Metagross: S > A+
Rotom-W A > A-
Celebi: A- > B+
Tangrowth: B- > B/B+
Hippowdon: A > A+
Gengar: A+ > A
Discussed all of these in previous posts and agree with them all. Will reiterate at some point if I feel the need to.
Going to have to disagree on this one. Personally, I've always liked slapping Ferrothorn onto teams as a convenient spikes setter with great defensive typing (easy check to water, dragon, etc...you get the point I'm sure as we all do this with Ferro), but it doesn't have the practical qualities and overall viability to rise to A+. While it is able to "resist" the fairy type, it's an easy set-up fodder for CM Clef (specifically Flamethrower variants, which fuck it over) and given the volume of pokemon with coverage or STAB moves to nail it in the current metagame (upwards of half of A+ and S tier, to put it in perspective), its vulnerability to moves like Scald, Knock Off (no lefties Ferro is annoying), etc. Ferrothorn uses Leech Seed to avoid being totally passive, which helps, but it is still throwing away some momentum and granting opportunities to a plethora of opposing threats upon coming in due to lacking speed, taunt, or anything of that sort (Gyro Ball and Power Whip can do decent damage to the right things, but it's obviously nothing to brag about). Add this to the fact that Skarmory, the tier's other primary steel type spiker which gives some competition to Ferro, is also in A and Ferrothorn itself hasn't became much better in recent weeks to warrant a rise when it was stablized in A beforehand and you get why I think it should stay in
A.
Managed to fit Cobalion onto a couple bulky offensive or straight offensive teams recently and while it doesn't wall a large portion of the metagame (hell, every special attacker gives it a hard time and many physical attackers - i.e: grounds - can also threaten it easily), it does have a cool niche when it comes to setting up SR, generating momentum, etc. (depending on set, it can run HP Ice to lure LandoT/Chomp or run Taunt to prevent opposing set-up) and it can wall a couple of highly ranked threats such as Weavile, Bisharp, non-eq/fire fang Mega Aero (can shrug off a hit or two regardless), and (Mega) Scizor (although it needs taunt to prevent it from giving free SDs to opposing Scizor). Overall, I feel that Cobalion is a lackluster pokemon in the metagame with very limited use, but it can fit into teams and fulfill a couple of key roles such as the aforementioned utility and checking duties, so I wouldn't mind it rising to B- given the fact that a lot of other generally mediocre, but sometimes useful pokemon reside in
B- currently.
Honestly, Mega Diancie just doesn't break through many teams currently, especially bulky ones, and it usually relies a lot upon protect, so CM isn't ever seen and RP isn't too common, either. It can pose as a lure to Scizor/Ferro with HP Fire, which is potentially useful with proper team support (I like using it with regular Gyarados, for example), but generally speaking the mindgames that come with having a Magic Bounce user, some moderate offensive pressure, and a fast offensive fairy is all you're getting with Mega Diancie in return for your mega slot. Looking at the other megas in A+ rank: Gyara, Lop, Sab, and Sciz. Gyara has the ability to sweep a lot of teams, especially with a lure or two working in conjunction with it, and I feel that it has the ability to break through and actually go somewhere far more often than Mega Diancie does (I may be looking at these two in comparison in a bit of a linear fashion, but I think it's still a valid comparison here). Lop is the epitome of anti-offense currently, imo, and it does a lot of damage with a lot of speed and it's pretty convenient to use, too. With PuP, it can fuck over opposing Hippo users or non-counter Skarm users if it is played wisely, too, so I feel like Lop is one of the top 5 megas in the tier and it does a much better job threatening things than Mega Diancie does. Sableye fulfills a defensive niche and I rarely use it, so I won't speak on this. Scizor, on the contrary, can be both a defensive and offensive presence on teams; given the fact that it can wall such a substantial portion of the metagame while also supporting, sweeping, and crippling many things, I can easily say that Mega Scizor should be higher than Mega Diancie in viability. Looking at it all in perspective and Mega Diancie simply isn't good enough in comparison to other A+ megas to stay in A+ and as a mon overall, I'm just not too impressed, so
A is the right place for it I suppose.