1.
Yveltal easily has the highest amount of utility and least opportunity cost among its B+rethen. I honestly think that it
should stay in A- but if it stays here it should stay ranked above all of B+. Yveltal can be adjusted to meet a team's needs pretty efficiently, with it being able to run its offensive set, which on paper is a huge threat to balance which usually lack something that resists both Flying and boosted Dark STABs. Its Atk is just as high as SpA base stat-wise, making Knock Off and Sucker Punch an answer to usual switch ins. While it's defensive set is much more niche, it punishes top tier dangerous setup sweepers like Salamence and Ekiller. Dark Aura boosted Sucker Punch also boasts as the most powerful priority in the metagame, securing an above average niche in beating offensive teams. Access to Taunt + Roost give it a nice ability to break Stall while being able to beat out the only thing that threatens the Taunt + Roost combo, Sableye. Hell, I've even tried Substitute which is surprisingly effective due to its massive HP stat. While it's 99 base speed is a pretty good tier for Ubers, sets almost never run max speed due to the need for investment in HP, Attack, and SpA but a lot of <90 Spe threats don't run max speed so I don't think that makes too much of a difference. Seeing as I've been spewing praise at it, I might as well throw some cons out there. Setup fodder for the most threatening sweeper in ther tier, Xerneas is a rather high risk to be adding to any team. The few threats that hit above 100 Spe are massive threats like Darkrai that Yveltal gives a free Dark Void. It also is susceptible to every status aliment, giving Klefki teams free Spikes/Toxic without Heat Wave which is kind of a bad option imo. It also fails to get a lot of 2HKOs on big threats like several non Ghost Arceus forms and Primal Ogre, which I think is only held back by the abundance of Groudon in this metagame. Other than that, nothing really is especially bad about Yveltal, besides being better on paper than it usually is in practice, but even then not terribly so. Either way, it clearly has less opportunity cost and is less niche than any other pokemon in B+.
2.
Dialga is the next most consistent out of the bunch here. It provides an alternative method of Stealth Rocks that you don't have to slap on PDon and has its SpD spread which is a pretty decent secondary switch in to Kyogre. It also has a plethora of coverage moves it can use as a pretty good lure to certain top threats. Stone Edge with only a bit of attack investment (about 60 with neutral nature) OHKOs Ho-ohs, which are usually enticed to switch in on a Dialga, especially after a Draco Meteor drop. Draco + Shuca Berry makes it safe to beat Salamence 1v1, although switching in isn't a guarantee. Dragon/Steel is a pretty unique and decent defensive typing. Not too much to say about it; Dialga has an expansive movepool to lure many of ORAS's top threats and with that I think that's good enough to justify its use and standing at the top of B+.
3.
Skymin sits here because it has great potential as a wallbreaker due to the very likely chance that a 140 base power STAB Seed Flare will instantly halve a targets SpDef. Grass is a pretty good offensive typing especially in a metagame dominated by Primals and lack of good grass resists besides Ho-oh. The SubSeed set is also pretty cool, its very good at getting off chip damage and plus like what's stall's counter for it lol. it also sits at a great speed tier, 127 is above 90% of the metagame besides Mewtwo forms and already evolved MegaGar and the few scarf threats. The only bad thing about it it that it contributes absolutely no defensive synergy to your team, only having a resist to fighting, grass, ground immunity and water which the latter doesn't exactly let you switch into Primals or Ground/Waterceus. Paired with lackluster defensive stats (besides the 100 HP but even then). Despite the ez SpD drops with Seed Flare, it misses out on a lot of common OHKOs it needs to get to not just die. Imo it works best when paired with lots of hazards to increase its OHKO capabilities. Momentum grabbing moves are also very useful for it for Skymin to get in without damage, but U-turn and Volt Switch are pretty uncommon among threats in the tier.
But how bad can it be when you can luck everything anyway.
4.
Skarmory is here because it's a really good mon at doing what it's supposed to do, but unfortunately not much else. It makes a great switch in to non Lava Plume Pdon, Salamence, Ekiller, Groundceus, and gets up Spikes and phazing. Toxic variants also directly threaten fat Arceii and Lugia, while Counter variants can outright kill physical sweepers by surprise. Spikes is beautiful in this metagame and forces your opponent to (likely) Defog or (less likely and spin-blockable) Rapid Spin all the hazards off the field, effectively reducing the pressure on your team as well. Skarmory is good at neutralizing strong physical threats for your team and getting up Spikes for your team. It doesn't check much but it's incredibly effective at the stuff it does stop, Along with Spikes being incredibly useful of course.
5.
MM2Y is my next pick because of its ability to 1- check Darkrai (offensively) and 2- run pretty much any coverage move your team needs. It hits harder than reg LO Mewtwo, though the opportunity cost of another mega + slightly weaker Mewtwo is usually less than devoting your mega to MM2Y. I think a lot of people discredit Y for being a "shaky" Darkrai check. There isn't exactly a plethora of sturdy Darkrai checks and the fact that Y can stop it from clicking Dark Void and then Nasty Plot is pretty big. It's downfall really is devoting your mega to something with such poor defensive typing- Psychic typing with no defense investment isn't going to be switching comfortably into literally any of the top threats. Even so, 106 / 70 / 120 Defenses isn't bad (on the special side) and can usually switch into a few non boosted neutral moves (and it even gets Recover lol). It's lack of useful resists is what really holds it back. Even with the monstrous offensive capability, many top threats carry offensive power so high that its high HP and SpD are rendered almost useless. It excels against passive teams however; there's nearly no safe counters to it besides MSableye, which doesn't exactly want to switch in on 194 SpA when the threats it checks force it to run 252 HP/ 252 Def. Taunt, Wisp, and T-wave are also some nice examples of utility it can use when it forces switches. Unless you're basing your team with Mega Mewtwo, it doesn't really find a good spot on teams due to no defensive value and the cost of using MM2Y is higher than say MMence + LO Mewtwo, which will allow your team to develop more versatility, and then if you choose Y then you kinda end up limiting your teambuilding.
6.
Tyranitar is a staple for stall to control the damage that Mega Gengar could cause. However, I feel outside of this, no one ever thinks "oh wow TTar would be a perfect rocker for my team". It checks Ho-oh like once and then gets burned and can't stop it after that. Being able to stop Gengar is huge, but it gets up rocks and dies in a lot of other situations. The RestTalk set is an option but it usually is even more passive and the rocks have to be designated to something else. It fits great on fat teams that get decimated by Gengar otherwise. It also of course has a nice role in providing sand for Excadrill. Sand isn't exactly unviable due to Excadrill 2HKOing the Primals that would seek to change the weather.
7.
Excadrill is only slightly lower than TTar due to sand. However, other than that, it's in no way a staple to any playstyle and needs TTar for sand. It has a small niche as a guaranteed Stealth Rocker with Mold Breaker but there's usually much more effiecient mons to use that can get rocks up. Also outspeeding GeoXern under sand its certanly not bad, just fitting on only one playstyle is kind of limiting figuring that the weather in ORAS Ubers changes to Sun a lot.
8.
I think a lot of people are in consensus that Mega Kang is the lowest among the B+ ranks. Toxic Spikes teams like Kangaskhan to rack up chip damage with its good priorities in Fake Out and Sucker Punch. Without Toxic Spikes you're probably better off just running Mega Mence as it beats down walls harder, has reliable recovery, stallbreaking abilities, better boosting and not hard walled by Ghostceus.
