Jirachi should definitely move up. It is a great mon on both stall and balance alike right now because it checks so many specially attacking threats in the meta, especially Mega Gardevoir. It's a great tool to wear your opponent's team down by statusing it with poison, paralysis, and flinching. Furthermore, it can be a wonderful support mon since it can learn Wish as well as Healing Wish.
Mega Houndoom I don't have much experience myself with, but I have watched several good players use it as well as playing against it with competent players. I can totally see it rising with the huuuuge rise of Mew, and Houndoom is pretty much a safeproof counter to that. It also counters Wow + taunt Gengar and has a great speed tier after Mega Evolving.
Mega Absol needs to move down. I don't recall having ever seen a decent player use this thing in ages. It was semi-decent during the Deo period I guess since it destroyed the Deo/Aeg/Sharp core but now two of those mons are banned and its just really bad right now. Horrendous bulk and the fact that it requires a crucial turn to mega evolve to get its desired speed tier is depressing.
Agree with Doublade. C+ is a really good place for it right now because it has an incredible niche on stall. It beats many powerful wallbreakers in just one slot, leaving your stall team to have 5 more spots to wall the rest of the metagame which is extremely beneficial. Don't move it up more than C+ tho because it's basically next to deadweight if the opposing team doesn't have one of those specific wallbreaking megas.
Agree with Blissey as well, move it down. It's outclassed at everything. Chansey tanks better hits than it, there are way better Landorus counters such as spdef gliscor and spdef mandibuzz, it has 0 offensive pressence and gives up way too many free turns to be effective.
I DISAGREE WITH WEAVILE MOVING UP. Weavile should stay the rank it is. Even tho it has an incredible speed tier allowing it to dispatch HO with relative few trouble, it is walled utterly by some of the most common and powerful threats. And giving these things a switch in is never good. Clefable, Keldeo, Azumarill, Mega Scizor, Zard X, Mega Hera all give 2 shits about it and now you need another mon on your team to deal with these aforementioned threats.
Ferrothorn still has some amazing defensive and support utility going for it, but it is not adapting well to this meta at all. I feel like everything in the meta has their guns pointed at Ferro atm... HP Fire Latis, Mag skyrocketing in usage overnight, HP Fire Greninja, Clefable can literally turn it into set up bait. It's still a good mon, but it no longer deserves the A+ ranking. Move it down.
LANDO-T SHOULD REMAIN A+. Everyone should know that usage does not equal viability by now. Even though you can pretty much slap Lando-T on any given team as a glue and offensive pivot, it neither poses much of an offensive threat nor a defensive threat. The two most common sets atm (Bulky SR and Scarf) are near useless vs any stall. The bulky SR set tanks hits well, yes, but it has no recovery allowing it to get worn down rather fast. The mons it beats (Zard X and Terrakion mainly) are declining in usage. Pinsir runs hyper cutter so it can't switch in on that well at all. Scarf Lando-T doesn't appreciate the transition of the previously fast paced HO meta to a more bulky offensive meta.
Move Magnezone up, of course. I'd even push to have this thing go to A. It's a great partner to birdspam teams because they appreciate its ability to trap steels. Even if skarm carries Shed Shell you can still get a free momentum switch via volt switch. Ironically, it's also great at combating bird spam teams as well with its choice scarf set, so its nowhere useless against offensive teams. Theres also that pretty cool magnet rise + air balloon set that gets a guaranteed kill on Exca which is really sweet.
Drop Landorus from S, it doesn't deserve it anymore. Too slow to be effective vs most offensive teams which outspeed and KO. Often in HO vs HO battles, I feel like I use Landorus as death fodder more than anything else. It's no longer the terror vs stall teams as it once was, since nearly every stall team has an answer for it now, such as spdef dnite or cress. Landorus is the best vs balanced teams, but typically, most of the stuff Lando does outspeed vs balance are bulky enough to tank a hit and KO back (i.e. Manaphy, Zard Y)
I never understood why Breloom was A- rank in the first place, so i definiely agree on moving it down. It's pretty much dead weight against any team that has a bulky grass like Mega Venu (hint hint ALL stall teams and most balance teams). Sash Mamo is a really popular lead for HO teams right now and it beats loom. The popularity of Lando-T and birdspam atm also means Breloom's effectiveness in OU isn't that good.
Drop Kube. Too slow to be much effective vs offense where everything outspeeds and KOes (like landorus). Most stall teams have common answers to this as well now. The increasing popularity of Mega Scizor, Clefable, Mega Garde, Mega Hera, Mega Medi, and jirachi don't help.
Mandibuzz is pretty shit right now. After Aegi's ban it lost one of its biggest niches. Right now the only reason to use mandi is for defog support, and i'd say its pretty outclassed at that. It gives free switches to many powerful threats right now which sometimes make it a liability to have on your team (like M Hera or M Garde)
In all honesty I haven't seen Mence used at all or played against it much so I can't really say anything about this, but uhh i don't think it deserves to move up cuz its pretty outclassed by every other dragon in OU. Hell, i'd use Haxorus over this
Tangrowth should move up, it's a really cool mon right now. It's a great pivot to stuff like Lando-t and rotom-w which is always good so they don't quickly wear down your team, it makes sure breloom doesn't cripple a mon, and it hardwalls Exca. hp fire lets it kinda check non bug bite scizor as well
Celebi is good in the current metagame and so it deserves to go up. It has a great niche on stall teams as an option to counter keldeo, azu, rotom-w, landorus, thundy. its also pretty unpredictable since it can run offensive LO sets or BP ones. I wouldn't rank it any higher than it is tho since it basically invites all bird spam members to come in against it for free
Move aggron down. Everytime I use it i just think (why dont i just use rhyperior). like seriously, i think rhyperior outclasses it completely except for countering bisharp and scizor. no healing at all, no offensive presence, and too passive. no one even uses it anyway.
Politoed deserves the A- ranking. Rain is so good in this meta, it destroys stall + HO alike when they're not unprepared. After deo-s ban, ALL rain teams pretty much are forced to have this thing too, which should only further bump it up. kingdra is by far the best rain abuser imo.
sylveon has some cool niches over clefable that allows it to be bumped up. clefable needs to run a mixed or specially defensive spread to tank the hits of thundy, greninja, and landorus well, which lowers its physical bulkiness greatly. sylveon doesnt need to run spdef investment and still tanks hits from those easily, allowing it to maximize its physical defense. it hits way harder and goes through subs. Basically, if your clefable doesn't have CM, i'd change it to sylveon. theres also the specs set which i never used but i heard its pretty good?
DISAGREE WITH SKARM MOVING DOWN. Just cuz Mag is popular as ever doesnt mean skarm should drop. if anything, its defensive utility is valued even more right now because of how popular bird spam and double bunny spam are. Just run shed shell on it, dont let it get knocked off, and skarm can still pull its weight extremely well.
Victini is good, move it up. It can function as a really powerful wallbreaker with the PuP set, can check some of the most powerful threats with its stall set, and can sweep on TR teams. Also Final Gambit spam is becoming pretty popular atm (really TFL?_?) so i guess it fits on those teams as well.