I was away for the weekend so I haven't gotten to post yet. Some thoughts.
-> A+. First thing, although I know it's off-topic, TRC recommended I post. Mega Charizard X in no way, shape, or form should stay in S Rank. TRC expressed that he was rather unsure about where he wanted to rank it, in any case. I'm interested to hear what
ben gay has to say, in any case, but here goes. The first and most immediate issue with Mega Charizard X is that its bulky Will-O-Wisp set is practically unviable in the current metagame. That's not to say that it can't work effectively, but the opportunity cost of using it over Mega Sableye or Mega Slowbro as a defensive Mega is simply far too high in order to justify its use as a defensive Pokemon. You can't even claim it has some sort of niche as a breaker, because Prankster Will-O-Wisp and difficult-to-break setup win conditions are certainly more effective as breakers. As far as DD is concerned, when you might say that the metagame is less prepared for it, this is more because of bad teambuilding than anything else. If anything, the increase in sand's popularity and rise of Pokemon like Scarf Keldeo, defensive vs Scarf Landorus-T, and Scarf Latios are rather major negatives for it.
The other problem is that it's competing far more for that slot as an ultra threatening DDer than before. Obviously there's Mega Salamence. If you think that's an unfair comparison, then take Mega Altaria. Mega Altaria boasts quite a bit over Mega Charizard X. It has far more bulk, objectively superior typing, and beats Pokemon like Slowbro, Heatran without even running EQ, Landorus-T, non-WW Hippowdon, and Scarf Latios/Keldeo. While it can have problems with Steel-types eg Skarmory and Ferrothorn, it has an option to beat these (Fire Blast), and these are fairly easy to remove given the right kind of support. It's much more difficult to contend with removing a Pokemon like Slowbro just to consider sweeping. Furthermore, Mega Altaria has the option to run multiple variants of its DD set, including the following: physically defensive, specially defensive, bulky offensive (248 HP with some Atk EVs + Adamant), all-out offensive, coverage moves (Fire Blast/EQ), and support/status prevention options (Heal Bell/Substitute). This isn't even mentioning the possibility to run specially based/mixed sets. Mega Charizard X boasts nowhere near this level of variety to its sets and utility for its team. Besides Mega Altaria, there's also an improved Mega Gyarados to contend with. Suffice it to say, Mega Charizard X has pretty objectively gotten worse as a result of the shifts in ORAS. Dropping it to A+ is very fair to it and definitely appropriate.
-> S. I agree with S for Mega Sableye.
Flamer quoted my earlier post which goes a bit more in-depth and has some calcs that give a better picture of its bulk in the context of the OU metagame. If there's one thing that you should get from my post, it's that Mega Sableye brings control to stall teams that it's had in the past and hasn't had for XY, which is control in the hazard game. Hazards have been everything for beating stall this gen. With SR up, you could double on Chansey into Latios 2HKO range and break stall from there, and Spikes would just amplify this. Teams could be built in such a manner (CBB's team is the best example) that Defogging with a defensive Defogger would be virtually impossible, or at least prolonged to the point where the damage was already done. A reliable Magic Bouncer, as in it beats all but 2 of the SR setters (Clef Lando-I, and of those SR Clef can't stop CM Mega Sableye and Lando-I is common in favor of coverage or RP) and prevents Spikes users like Ferrothorn and Skarmory (Spikes Greninja is now uncommon because it has way too much coverage to run Spikes, plus this can be covered by a great partner called Tentacruel) from getting up their hazards. This combined with the anti-offense support of Prankster Will-O-Wisp and sheer devastation of the CM set as a sweeper makes Mega Sableye nothing short of incredible.
-> A. I don't agree with dropping Excadrill at all. If anything, ORAS has made sand better. Sure, it could be argued that the continuing popularity of Landorus-T and Rotom-W is a negative for it, but this is more than compensated for by all the fast new Pokemon that are slaughtered by it. Furthermore, SD Excadrill is an excellent way to help clear the way for the likes of Mega Gallade and Mega Altaria, and even LO Spin variants get to punish Mega Sableye pretty well. Sand is still going strong in ORAS, and Excadrill is at the forefront of it in stomping some of these fast, frail Pokemon and providing an invaluable offensive support.
-> A+. I'm grouping these together because they're pretty similar in how their roles impact the metagame. Rotom-W and Ferrothorn, along with Landorus-T which is already in A+, are the foundations for bulky offense and offensively minded balance in this metagame. These two Pokemon provide an enormous amount of threat coverage and utility for the team that is simply unparalleled. Rotom-W provides a solid check to threats like Talonflame, Landorus-T, Garchomp, Azumarill, and Excadrill, while faring well against an unbelievable amount of physical and even some special threats in 1v1 scenarios. It provides an invaluable Ground immunity and pivot with Volt Switch, both of which are traits heavily desired by OU teams. Furthermore, with the following spread - 248 HP / 88 Def / 124 SpD / 48 Spe Bold - that I've been running, it can tank two Dark Pulses from Greninja with Leftovers recovery after Stealth Rock damage, allowing it to serve as a check to that if necessary. Rotom-W's utility as a pivot and check to all kinds of threatening Pokemon makes it more than worthy of A+ Rank.
Similarly, Ferrothorn's defensive utility is simply superb in the current metagame. While it could be argued that Magnezone is severely detrimental to it, there's always the option to run Shed Shell if you want to get around it (others like this, I don't because I feel it doesn't last as well as I want it to, but this is just a matter of personal opinion), and this does not outweigh the sheer amount of utility Ferrothorn provides. So long as it doesn't run HP Fire, Ferrothorn is one of the few Pokemon that is a relatively safe answer to Greninja with the mixed defensive spread (252/88+/168) or even better a Sassy nature. It provides hazards, it checks Latios (which is running less HP Fire in favor of Roost Defog from what I've seen as of late), it checks Azumarill, it checks non-Hammer Arm (aka the majority of) Mega Metagross, it checks Mega Altaria, it checks Mega Diancie, it checks the improved Mega Gyarados, it does all of these things...while being able to provide invaluable entry hazard support for teams in the form of Stealth Rock or Spikes stack. Ferrothorn is another bulky offense/balance building block that definitively belongs in A+ Rank.
-> A+. People sleeping on this mon...Mega Altaria is crazy good. While the competition of Mence is of course there and present, Mega Altaria certainly has some traits for it to stand out. It profits from one of the best defensive typings in the game of Pokemon, which is Fairy/Dragon. This combined with its bulk lets it serve as a check to a myriad of threats, such as Mega Heracross, Latios, Keldeo, Mega Lopunny, Mega Slowbro, and Mega Sceptile. It can't even be revenge killed by conventional Scarfers, such as Landorus-T, Keldeo, and Latios. This sheer amount of threat coverage, bulk, and resistances grants Mega Altaria a myriad of opportunities to set up and pull off sweeps. I talked about this a bit in my Mega Charizard X comments, but to rehash a bit, this variety includes all of the following:
- EV spreads: physically defensive, specially defensive, bulky offensive, and all-out offensive;
- Supportive options/status prevention: Heal Bell and Substitute;
- Coverage options: Fire Blast and Earthquake.
This variety of options offers significant customization opportunities for Mega Altaria based on the type of team and what its teammates are able to cover. With its common bulky Heal Bell mono-attacker set, Mega Altaria is able to defeat common defensive Pokemon like Slowbro and Landorus-T with relative ease. More offensive sets can threaten Pokemon like Heatran, Ferrothorn, and Skarmory in a more efficient/effective manner. Mega Altaria can also run an effective specially based mixed set of Hyper Voice / Fire Blast / Earthquake / Roost and function as an excellent breaker, or even with Return over Hyper Voice and a more physically biased EV spread to bluff a DD set/have that source of physical offense. The versatility, ease of setting up, and sweeping capability that Mega Altaria brings to the table is enormous and makes it more than worthy of A+ Rank in the current metagame.
-> A-. I actually made an ORAS team based around Mega Aerodactyl earlier last week, recognizing its potential and effectiveness in the current metagame. While it certainly proved effective, I have to say that some of the hype around it is a little over the top. The only real viable set for Mega Aerodactyl atm is 4 attacks coverage. Other sets, like Taunt + Roost, simply don't have the coverage needed to take out some of these threats around and function effectively. It can check a lot of Pokemon offensively, but it also has a debilitating Stealth Rock weakness for something that wants to come in and wreak some havoc rather frequently, and possesses few - if any - real switch-in opportunities that it can capitalize on. Mega Aerodactyl is also hard-stopped by Slowbro which is very common atm, misses important KOs on Pokemon like Latios especially because it's forced to run a Jolly nature, has issues breaking Mega Sableye, and can pretty much always be checked by offense due to the effectiveness of Scarf Landorus-T and Keldeo. A- Rank is a perfectly fine rank and more than acceptable for Mega Aerodactyl given its rather noticeable flaws from my use of it in the ORAS metagame.
-> A. Mega Latias is by-and-large extremely overhyped. The first and most immediate problem is that it's way too slow to set up. What this means is that it can't keep up with the pace and tempo of offensive teams like, say, Mega Slowbro or Mega Sableye, which each have their own ways of doing so (more immediate power, Sableye's Prankster Will-O-Wisp). A+ Rank - let alone S, which has been brought up - also means it's comparable to Pokemon like Mega Slowbro, potentially Mega Altaria, and Mega Gallade, which it simply is not. I'd rather see Mega Latias drop than go up in rank.
-> A- (Heracross) and B- (Medicham). I grouped these together because they're commonly referred to as the 'wallbreaking Megas'. I'll start with Mega Medicham, which is borderline unusable in the current metagame tbf and B- is being generous. There's a Pokemon called Mega Gallade and a Pokemon called Mega Lopunny around; why would I use Mega Medicham over either of these? If I use Mega Gallade, I've got a faster, bulkier Pokemon with crazy wallbreaking and sweeping potential that far outclasses that of Mega Medicham. If I use Mega Lopunny, I'm working with something weaker, but that smashes through the omnipresent Mega Sableye and is crazy fast with unresisted STAB coverage? Yes please. Mega Medicham is outclassed by two extremely solid ORAS Mega introductions. This is a pretty clear-cut case of opportunity cost and being eclipsed by other, better Pokemon.
Mega Heracross being higher in rank is simply because I can sympathize with the fact that teams are less prepared for Mega Heracross as a whole. I don't buy the whole 'stall teams have trouble with it now' because that's just poor building, but the decrease in Acro Scor on balance is certainly a huge positive for it in that Mega Heracross has gained some propensity to break vs balance. Mega Heracross also beats some common Pokemon like Mega Lopunny, Mega Beedrill, Mega Sceptile, Landorus-T, Mega Slowbro, and Greninja 1v1, giving it some legitimate defensive utility on teams.