I'm gonna make some noms mostly based off of what i've seen so far during olt. These changes may go back to normal once olt is over but i feel like for now these noms are pretty reasonable.
magearna up to A+
Although assault vest is still pretty good, that is not the reason this should rise back up to A+. The reason that this deserves a rise is that it is so popular and so good on all the hyper offense teams being spammed on the ladder right now. This thing is great on webs, dual screens, trick room, veil etc. Also, it has so many different sets it can run. Shift gear leftovers, shift gear any z move, offensive trick room, shift gear calm mind, and it can choose between fire steel ice electric fighting and fairy coverage. This mon is really great right now like it has always been and i think it should reflect this. (it is also really good on normal bulky offense teams as all these sets still work there.)
mega scizor to A+
I feel like right now mega scizor is the best mega in the whole tier, or at least very close. I believe that if mega latios should rise (which i absolutely think it should) that this should rise along with it. Curse mega scizor is actually so great as it can beat most balance teams once the bulky water/steel types is gone which is pretty easy to do with the prevelance of tapu bulu, zapdos, heatran, zygarde etc. It also kind of just beats a lot of hyper offense teams because it can set up on a lot of common physical attackers like landorus, zygarde, and even stuff like alolan ninetales. I really feel like this as well as mega latios should both rise up as i feel they are a step above every other mega in the tier.
Garchomp up to B
This is controversial but rocky helmet garchomp is in a really amazing spot. I talked about it a lot in my post over here:
https://www.smogon.com/forums/threads/usum-metagame-discussion.3621042/page-22 so just read that.
Jirachi up to B or even B+
This is just absolutely fantastic right now. It is so splashable and can fit on every style of team, even HO (but you really shouldn't use it there because offensive sets aren't great). Again, talked about it in my post here
https://www.smogon.com/forums/threads/usum-metagame-discussion.3621042/page-22 so read that and i would just like to add on to that a little bit. The fact that lele and magearna are getting more popular is great for this as it is one of the best checks to those right now. Also, i think that B- was just to low for it in the first place so this is a necessary rise in my eyes. Although it looks like a lot of things are unfavorable for it in the meta right now, if you have this on your team it will always put in work.
Blacephalon up to B
I know that everyone here loves to hate on this mon and it probably won't rise, but i'm gonna try my best to push for it because it really deserves one. I think it's best sets right now are sub calm mind z move speed boosting set or just normal sub calm mind z move spatk boosting set, but the normal scarf and specs sets are also still good. This mon is just so amazing and splashable on HO right now that it is really due for a rise. It can snowball unprepared teams and it pretty much beats stall by itself. Not to mention it is also great against balance and it is unpredictable with it's set. This thing really should rise to at least B- but i think B suits it more. Also, this is benefited by the rise in jirachi tapu bulu and scizor.
Mega gyara up to B+
This pokemon is always good during olt because hyper offense is always spammed during olt and this is amazing on hyper offense. It works on literally every kind of hyper offense and is the best mega pokemon on every kind of hyper offense (mega ttar is it's only real competition for that slot). It can either sweep late game with it's great bulk allowing it to set up dragon dances or it can break holes early in a game so it's teammates can sweep. With veil or screens up this is virtually impossible to OHKO and most of the time super effective attacks don't even 2HKO.
Serperior up to B- or higher
I don't really know what's changed for this other than the use of more HO teams that it's been great on, but the huge spike in usage as well as it's effectiveness on said HO teams is really great for this mon and it just seems very effective right now. The most popular set is sub glare leech seed leaf storm and it's pretty great and i guess people just discovered this mon's true potential and started using it and realized it is actually just a great pokemon right now.
tapu fini up to B+
This is a big rise but i think it is extremely, extremely well deserved. Tapu fini is definitely one of my favorite mons in the meta right now and it is absolutely fantastic. It is a great switch in and blanket check to almost everything right now, a great defogger, great at breaking through many prominent bulky cores, and provides amazing support to teams with misty terrain. Some meta changes that are good for it are the rises in zygarde and heatran (other than z bloom doom of course). I go more in depth in my post here
https://www.smogon.com/forums/threads/usum-metagame-discussion.3621042/page-22 so read that and please rise this at least to B but preferably to B+.
I am just going to give my opinion on a couple noms that have already been made:
muk up: yes
charizard x up: yes
clefable up: yes
alakazam up: yes
I am not at the top of the ladder right now so my views may be a little bit skewed but i feel like im at a high enough point where i have a good grasp of the meta and i am confident in all of these noms