Proposed Changes:
Arc-water to A: Over-rated, extremely common set but every team has several ways to beat it including steels, status is becoming more common and its just not as good at doing its job as it once was. I'd feel it would be good above Groundceus below deo-s.
Gira-O to A/A-: Basically what sweep said, its not that great at defogging cause of no recovery and its other sets aren't good enough to put it alongside Mega Gengar and Klefki. If A, bottom of A, if A- top of A-.
Lugia to A: Stall is just getting worse and worse and that means the same for Lugia. Almost every team has a steel type that can come in for free on it, there are a number of sets going around on pokemon lugia is intended to beat that it cant now (jolly sd pdon, jolly ray, ext) and Mega Gengar is arguably better than before with the rise in popularity of hex-spam teams, which Lugia really hates. Ideally below mega Diancie, above Gira-O.
Mega Sab to A-: This was probably a bit high in the first place, it stops some rocks but the metagame is really prepared for it right now and it cannot prevent rocks most of the time. Also because of the rocks situation, it can be easy to wear down, especially with things like Dazzling Gleam klefki becoming more popular to wear it down even more.I'd put it below Ray above Dragonceus.
Arc-ghost to A+: Ghostceus has seen a rise in popularity of the kind of teams it can decimate at +2 and is just generally more capable than an A ranking suggests. Also great to have an offensive check to Ekiller, Latios, Mewtwo and Kangaskhan. I'd have it above Klekfi but below Gengar, essentially taking Gira-O's place.
Deo-a to A/A+: Nuke. In a meta where scarfers are uncommon and priority users are obvious, this thing is an absolute train, especially with the rash sets that are more popular now. To paraphrase someone in the ubers skype, if the matchup is offense vs offense, and one of the teams has a deo-a, that team should win. If A, above Latios, if A+ below Klefki.
Dialga up to A-: A really good stealth rock setter that frees up the primal groudon slot, provides defensive synergy and can get rocks up from both bouncers, while beating almost every defog user in a one on one setting? A- at least. I'd have it between Yveltal and Dragceus.
mewtwo-y up to B+: This thing is really underrated right now, and with Mewtwo in A-, I feel this should rise to B+. Its not that much worse than its life orb form, and given the rise of rash deo-a, can actually turn the offense vs offense matchup in the favour of the mewtwo team. I feel this should go to between lando-t and skarmory personally, but I could see it slotting between Skarm and Skymin as well.
Blissey down to B-: Just like Lugia, this thing is worse now than it was a few months ago, stall in general is just really not great at the moment. As for specifically why it should drop, the defensive geoxerns with rest and block and stuff are more popular now than when the thread was closed and it turns blissey from a check into setup fodder. I actually feel B- in general should be re-ordered (along with B for that matter) and in that hypothetical I'd have it so it went Iceceus, Cloyster, Mega TTar, Blissey, Scolipede, Darkceus Greninja Blaziken Fairyceus. But in the order given, above Arceus-Dark I suppose.
Slowbro to C+: Slowbro's no worse than it was a few months ago, I just feel it was perhaps given too much credit. Dont care much on this one but it definitely looks more at home in C+ to me. Probably between Alomomola and Cresselia,
Tenta to become unlisted: The entire reason for this thread being unlocked was a discussion sparked by the latest ubers article when I saw tentacruel mentioned and thought it'd been pulled out of the writers ass. Turns out its actually ranked here and has an analysis... for some reason. Tentacruel is just not good enough at what it does to have a ranking, while it might be able to in theory, it has seen 0 tour use afaik, and on top of that gives threats like pdon and ray and ekiller and groundceus free setup 70% of the time. Also if you're using it as a spinner, it will get worn down really easily, to where it can no longer reliably set tspikes nor spin nor check things like Geoxern.
also Q.... yeah fuck it i'm not typing out that full name, you're massively over-rating Ditto. C- is being generous to it given how useless it can be in matchups outside of standard HO, and even in that matchup its more than possible to make ditto not as useful as you seem to think it is.