Gyarados (Mega): A -> A- no
In a meta filled with keldeo, ferro, and clefable, its understandable to question a drop, but mega gyarados, given the right support and partners, is monstrously good. It is by far the easiest mon in the tier to set up a dragon dance with, given its potential typing of mega or non-mega evolutions. The aforementioned are pretty easy to lure or wear down, and healing wish/hazard support isn't TOO bad considering latias can cover both and scarf rachi is super good glue for offense already. The taunt/dd set also smashes defensive builds as it sets up on mega sab and skarm (which usually pack iron head) with ease. Even after a dd, if you haven't mega evolved yet, things like scarf keldeo or scarf lando-t can't safely revenge kill you lest you predict their coverage and stay normal/mega evolve (predict superpower on scarf lanT and stay normal, or predict hp ele from keldeo and mevo). It's just way better than the likes of raikou and slowbro-mega.
Kyurem-Black: A -> A- no
Even with ice beam, earth power, and fusion bolt, it hits a really unique set of pokemon, being able to nail slowbro, skarm, mvenu, heatran, and hippo all at once, something that nothing else can do. The fun doesn't end there, LO iron head destroys any clefable after an ice beam, and hp fire can catch scizors and ferrothorns on the switch. Even Chansey is cleanly 2hko'd by LO outrage, leaving only the easily worn down tyranitar as the check. Granted that scarftar is getting very popular and is continuing to give kyu-b a tough time, its far from a reliable switch-in. Rocks also suck, and roost giving it longevity is a total myth; you're better off attacking 90% of the time as every switch-in is precious. But it also does a decent job of checking shit like mega manectric and manaphy, which is nice as many other wallbreakers can hardly offer much defensively. It's a decent threat to balance and has some defensive capability, its fine where it is.
Manectric (Mega): A -> A- no
Even tho hippo shuts this poor puppy down at team preview, and it really doesn't have much firepower behind it, its electric/fire/ice coverage in conjunction with its speed is just fantastic. The rising popularity of sand annoys it but it's still good enough to be placed among the ranks of gengar and mvenu.
Breloom: A- -> A no
While this thing is getting a ton of hype recently, AM covered pretty well why its not all so rosy for breloom. Once spore is used up (and its common to have some useless mon given matchup and all) it's very easy to handle and fit in several checks to it. It doesn't impose anything near the team constraint level of things like rotom-w, and while its good and all, it's just not on the level of tyranitar and skarm. It's fine where it is.
Starmie: A- -> A no
While hazards may have been getting more prevalent, it may make sense to give the best hazard remover a boost. The problem is that starmie itself still sucks. The defensive set is super super super passive, yes it can t-wave and do annoying shit in the last slot but scarftar plays 50/50s with it and it's extremely reliant on scald burns. Hell, bulky chomp can usually keep rocks up against starmie just because the poor thing kills itself when it rapid spins. The offensive sets are better, threatening offensive teams with some big coverage, analytic, and good speed, but that starmie still has no recovery and relies on hydro to do any kind of respectable neutral damage. I just feel like its still bad :[
Jirachi: A- -> A yes
scarfrachi is an amazing glue for offense and honestly a potent wincon lmao. Healing wish support is awesome and fast pivot with good typing to check fairies, dragons, and the works is just great. On the other end of the spectrum, sdef variants can tank even LO kyu-b's earth powers with wish+protect and easily wall big threats like CM lati, mgarde, diancie, mega lop sorta (with protect and all that), azu, alt, etc its super solid. In the middle, some ebelt lure sets mesh will with threats like char-x when it weilds options like hp ground, energy ball, icy wind, hp fire, thunderbolt, and other cool shit (i find eball better than gknot so that u can hit rotom-w and still hit slowbro/hippo hard enough). Popularity of bulkychomp, lando-t, and heatran hurt it but its utility is too valuable to pass up, bump it up.
Aerodactyl (Mega): A- > B+ yes
Ice fang is damn near mandatory on this now, and the popularity of sand doesn't do it any favors either. Garchomp/lando-t are at an all time high and it's really just not a great time to use maero lol. Popular meta trends are REALLY against its favor and checking talon and being fast and having coverage and all that is nice but it's simply not strong enough to break through balance and not fast enough to avoid the revenge kill from scarf lando-t/keld/rachi or exca in sand. Drop it :[
Latias (Mega): B+ -> A- yes
I've gotten around to using mlatias more and i've gotta say its spike in tour usage is no surprise. Given how consistent balance can be, its popular in tours, and mlatias is a goddam godsend for balance teams. With boltbeam coverage it checks the hard to cover SD lando-t, TG manaphy, SD gliscor, and even the underrated SD crawdaunt for balance, alongside already beating shit like char-y, thundy, keldeo. It's stupidly bulky and sets like t-wave, calm mind, and reflect type are all really annoying or dangerous. There's a good reason the once shining manaphy has only been used 3 times in SPL so far, and this thing's about 80% of the reason lol
Sharpedo (Mega): B -> B- yes
It's "easier" to set up than mega gyarados but holy shit is it weaker. While protect speed boost means that no free-turns are needed to start cleaning, you need to weaken SO MUCH SHIT in order to actually clean. Get rid of talon, breloom, exca, scarf rachi, scarf lando-t, scarf keldeo, thundurus, klefki and weaken mega altaria, clefable, keldeo, ferrothorn, azumarill, bisharp, manaphy, msab, mzor, kyu-b, skarmory, rotom-w, mvenu, magnezone, amoonguss, tangrowth I think you get my point by now holy fucking shit you never actually clean with this thing. You also only have one shot to clean, even healing wish support won't save you like it would save malt or mgyara or zardx. It's strong jaw crunch is pretty nice, i'll give it that, but it's WAY too weak and needs WAY too much weakened to actually clean. Just drop it man
Crawdaunt: B- -> B yes
your standard good ol' msab/skarm/chansey/quag/amoong/scarftar stall gets fucking 6-0d by this force of nature. This thing's absurdly strong against slower builds, it plows through resists like paper and sends even bulky things like clefable and ferrothorn to the other side at +2. It's really really easy to handle with offense, stuff like keldeo, breloom, mlop, lati, etc take jet and kill back with no sweat. In this regard, its very matchup based, so I doubt it should move up farther only because its so inconsistent, but goddam when its facing slow teams it seriously carries its weight.