Azumarill: Yeah I kind of support this one. Azumarill is really amazing mon in theory, but it can only run one set at a time and they all have pretty big shortcomings. Assault Vest is really not that good, most Greninjas run grass moves and Latios usually runs psyshock. This is heralded as the best Azumarill, I'm not exactly sure why. It is nice to have a bulky pivot, but the set sacrifices the power to break through bulky mons pretty quickly. No regenerator or whatever means Azumarill gets worn down really quick, it's not an assault vest mon I love. In addition, a lot of its resistances are more useful on the physical side (Gyarados, CharX.) TLDR Azumarill with AV is kind oh bleh because it's stopped by most bulky pokemon, it's easy to wear down, and lots of things can get around it (it's become a thing special attackers prepare for.) Choice Band is probably my personal favorite because it has the power to break defensive threats. However, it is stopped dead by Mega Venusaur or Amoonguss (both really common on stall) or Ferrothorn if you don't run superpower. Without the bulk from AV, special attackers can run over it pretty easily after a bit of prior damage. Personally, whenever I use Azumarill I use this as I find it to be threatening without being suicidal. However, hyper offense will dispatch of it quickly, and stall will have a counter, making its good matchups limited. Belly Drum is great for hyper offense, but all Azumarill can really do before drumming is play rough, which doesn't hit everything that well, and unboosted is kind of weak anyways. Drumming requires Azumarill to be in a pretty good scenario where it can kill the mon its facing with an aqua jet and survive an attack + drum 50%. If you try to use Azumarill's typing defensively, your Sitrus Berry will probably get burned, which makes set up near impossible. To me, Azumarill is not amazing because each set has a lot of flaws (I'm not addressing thick fat/sap sipper because that's practically a different mon) and you basically have to pick your poison. No matter what you choose, Azumarill will always have Venusaur as a hard counter, which makes it dead weight a portion of the time. It does have great typing and pretty solid stats, but it's slow and gets worn down quickly, and it's not powerufl enough without a CB or drum boost.Important changes to discuss:
Azumarill: S ---> A+
Thundurus: S ---> A+
Latios: A+ ---> S
Tyranitar: A ---> A-
Mega Gardevoir: A ---> A+
Mega Alakazam: A- ---> B+
Mega Aerodactyl: A- ---> B+
Quagsire: B ---> B-
Thundurus: Thundurus has a simple issue: if it's LO it dies really fast (especially with sandstorm and/or stelath rock in play) and is quickly in range for priority. Without a life orb (leftovers) it has a lot more staying power, but a lot less destructive power. This is especially apparent in hidden power, which is pretty pathetic without a life orb at times. To illustrate how weak this is, take into account thunderbolt has less than a 20% chance to OHKO standard CB azumarill, and is not guaranteed after rocks! HP Flying is so weak that it doesn't always 2HKO physically defensive venusaur, only pulling through about a third of the time. HP ice cannot always OHKO timid landorus, and flat out fails to KO landorus-t (who does more back with stone edge.) So life orb is generally a better choice. Thundurus is known for his ability to paralyze fast sweepers, but once those sweepers have set up, he dies to accomplish this task unless parahax occurs. This is a trade only HO teams can really make, balance teams are going to be very disadvantaged after this. However, Thundurus does do his job usually, so he is undeniably a good offensive support. Now, let's assess his offensive capabilities. Thundurus cannot break a lot of pokemon in OU that are fairly common, even with the pretty essential life orb. His movepool is amazing (knock off, superpower, grass knot, focus blast) but his moves are limited, making him always have definitive counters. Without knock off, Latias with slight hp investment is a good switch in. Without grass knot, Quagsire, Gastrodon, and Hippowdon have a field day. Without HP flying, Venusaur and Amoonguss have an easy time (and even with it sort of.) Without focus blast, you're using the mon wrong as well- Ferrothorn, Excadrill, Tyranitar, etc. are important to stop. Superpower is not as good, but kind of works. If you want prankster support, you sort of need focus blast and thunderbolt (superpower kind of works as well.) So from HP ice, HP flying, and knock off only one move can be picked- and all have serious shortcomings. Mixed Thundurus is something else, but it's a mediocre wallbreaker that really only has speed as an advantage, which is pretty nice when facing Latis, Keldeo, etc. Thundurus has a lot of versatility, but it also has some serious flaws, so I think it should move down.
Latios: I think I back this one, but my opinion is not definite. My first thought here is how easy Latios is to use in teambuilding. I honestly build very few teams without him or Latias (the choice made on how well the rest of my team checks Keldeo primarily.) If you want hazard removal, your options are very limited right now. Excadrill has rapid spin, and good power, but the way the mon works isn't for everyone (or every team.) Zapdos and Skarmory (is Mandibuzz still relevant??) aren't very good right now, they don't do much outside of walling Pinsir and a few others. Skarmory gets grounds like Excadrill while Zapdos walls...Scizor? Honestly whatever rank Zap is in is too high. Anyways, the Lati twins are far and away the best option for hazard removal, which is excellent if you want to use stuf like Charizard, Talonflame, and Pinsir. Excadrill is close, but I honesty think he doesn't fit too well with Charizard-Y or Talonflame. Latios and Latias are many things defensively- they resist water, fire, fighting, grass, ground, electric, and psychic. They completely thrash non Knock Off Landorus and non Dragon Pulse Charizard-Y, and are the almost sole reason those things even exist. The speed tier is awesome for revenging Keldeo and Terrakion, and fast enough to quash a Mega Heracross or Medicham sweep. Forcing those mons to switch out makes defog easy and predicting switch ins is not difficult. Roost is also a good move on switches so Keldeo can't wear you down. Draco Meteor is strong and gets rid of most non fairy/steel things. Latios has a lot of coverage, and can bend his moveset to beat anything but Clefable and Chansey. Psyshock/Draco Meteor is the most common, but fails against steels. Personally, I love hidden power fighting, because it gets around the biggest threat to Latios: pursuit (KOes Bisharp, 2HKO Tyranitar.) Earthquake hits Heatran, Thunderbolt hits waters, HP fire hits ferrothorn. There are really so many options that allow Latios to be welded into any team. If you forgo Defog (don't need to, or Excadrill is present) or Roost (hyper offense go!) even more moves can be used, and three moves can form a pretty awesome trifecta of coverage. I like HP Fighting/Draco Meteor/Thunderbolt when I don't need defog and roost. In summary, Latios is good for revenge killing and the best hazard remover, fits into near every team. Latias is good as well, but less power so I think only Latios should move up (also then the entire S rank remains blue.)
will respond to to others later.