TEXT WALL INCOMING
Alright I guess I might as well give my two cents, although it'll probably get washed away rather quickly in the sea of posts. I'm mostly going to focus on Genesect as of now, and I'll probably touch on Deo-S later because I'm much more on the fence with it. I'm not even gonna bother saying anything about Mega Luc, because no offense, if you've been playing the OU meta for these last few months you should know damn well just how dumb it is. Both sets combined have completely different counters, the special set being extremely limited to stuff like specially defensive Zapdos and a few really niche things that no one wants to use. To be honest, everything that I wanted to say about it has been said, so I'll just leave it at that.
Okay so Genesect. We all know how amazing this fucker is, and it's quite obvious that he's the best Pokemon in OU at the moment, aside from Mega Lucario. It can run like 8 sets, it's pretty unpredictable, hits pretty hard, and gains momentum like nobody's business. Now I'm not denying that these traits can raise a few eyebrows as to whether or not its healthy in the metagame, but I'd like to give my honest opinion on the subject on banning Genesect itself, and how I feel that some people are trying to ban it for the wrong reasons.
Personally, I despise the versatile = broken mentality. To me, this doesn't suffice for a strong enough reasoning in banning a Pokemon. Versatility doesn't necessarily have anything to do with how the Pokemon has a negative impact on the metagame. There are lots of Pokemon that are extremely versatile and can run a number of successful sets in the metagame, but that doesn't necessarily make them broken because of that. A perfect example of a Pokemon that was incredibly versatile last gen but wasn't even close to being broken was Jirachi. Jirachi could run a total of 7 very viable sets at the end of BW2, and it even ran a few other sets that just never ended up making it to the analysis, such as the SR lead set, Shuca sets, etc. Not only was Jirachi incredibly dangerous and versatile, but the ability to run all of these sets made it unpredictable as fuck, and its movepool was almost just as crazy as Genesects. The only issue was, each set had very similar checks and counters, meaning that no matter what set Jirachi would run, most of its sets were all threatened by the same things. Genesect is similar in that retrospect, because while it has incredible versatility, it's still checked and countered by the same pool of Pokemon, for the most part of course. Genesect can still run specific moves like HP Ground to get around Heatran or Thunderbolt for Azumarill, but Jirachi did that too with Shuca Berry to beat Mamoswine and Landorus. Of course BW Jirachi and XY Genesect are two completely different Pokemon, but I was just using that as an example to prove my point that versatility alone does not make a Pokemon broken. While Jirachi was versatile and unpredictable, none of its sets were unhealthy on the metagame, nor did any of it sets centralize the tier in any way. I'm not saying that versatility can't play a role in the banning of a Pokemon, but I refuse to believe that it's justifiable to ban a Pokemon solely for this reason.
If we're going to ban Genesect, we need to ban it for the right reasons; by looking at its sets individually and seeing if a majority of these sets have a more negative impact on the metagame than positives. Download is an absurd ability because it makes it incredibly easy for Genesect to revenge kill with its plethora of coverage moves, and with the added Attack boost it's able to deal heavy damage to Pokemon with U-turn while still grabbing momentum. This makes it relatively easy for Genesect to not only give its teammates easy set up opportunities, but it can also weaken down defensive cores fairly quickly, making it easier for a teammate to sweep after a few turns of this.
The Choice Scarf set is able to revenge kill better than anything this tier has to offer. Depending on what coverage moves it run, it can check many different kinds of Pokemon that may threaten your team, such as Garchomp, Lucario, Landorus, Azumarill, Togekiss, and Tyranitar. This makes it a wonderful fit for most teams, because it is able to handle a lot of offensive Pokemon that give most teams trouble. On top of that, a fast U-turn allows it to gain momentum on a wide range of Pokemon, while wearing down defensive cores and picking off Psychic-types. To be honest, I think this set is quite healthy in the current metagame. While its ability to bring an insane amount of momentum to teams is absurd, it's one of the only good users of Choice Scarf this generation. This is mostly caused by the shift towards bulky offense, which makes it much more difficult for Pokemon function with just 4 moves on top of being locked into them. Also, a lot of Pokemon that were commonly wielding the Choice Scarf were of the Dragon- or Fighting-type, and with the introduction of Fairy- and Ghost-types this generation, it's much harder for the likes of Terrakion, Garchomp, Keldeo, and Latios to revenge kill, to a point where it's not worth it. Talonflame is an incredible revenge killer, but it requires much more support than your average Scarfer due to its SR weakness, nasty recoil, and its common counters are on almost every team. I feel that without Choice Scarf Genesect, offensive teams in particular will struggle to deal with set up sweepers, because they will be so limited to what they can use to revenge kill. I'm not saying that offensive teams couldn't function without Scarf Genesect, but they'll have a much harder time finding ways to deal with said threats because of this.
To be perfectly honest, I've never really seen or used Physical Shift Gear Genesect, mostly because I've found so much more use out of its other sets. I don't really want to say too much about this set because I don't have hardly any experience, but from what I've heard it's pretty manageable. A lot of it depends on what it runs, but it's always going to be walled by Heatran, and even Landorus-T or Gliscor if you choose to run Iron head over Ice Beam. A +1 Blaze Kick fails to even come close to OHKOing Skarmory, which means that Flamethrower is probably a better option anyway. Speaking of which, it depends heavily on the Attack boost to get going, or else in all honestly I'd rather just use CB or the good ole' fashioned RP all out special set, which has more coverage overall and doesn't need the boost as much because of its insane coverage. Both sets are still phenomenal sweepers, but only the special sweeping sets seem to be the more metagame threatening. Speaking of Choice Band, this is the set that I honestly think is pretty unhealthy for the metagame. While it is still walled by Heatran and the like, a +1 CB U-turn or Iron head is going to dent so many things it's not even funny. On top of that, it can use Flamethrower or Ice beam to bypass bulky defensive Pokemon like Landorus-T, Skarmory, or Aegislash. It's just so easy to wear shit down, to a point where it's almost frustrating. Unlike the Shift Gear set, it doesn't need to set up, and can immediately start spamming +2 ExtremeSpeeds Turn 1 if it wants to. This set may be slower, but it lacks a few more checks because of ExtremeSpeed, and it's no longer walled to hell by Chansey. This set literally does nothing to help the metagame in anyway other than to just make it easier to wear shit down.
All in all, Genesect is putting me on the fence. It has a some great merits in the metagame, but it certainly has its negatives impacts on the metagame, just like all suspects usually have. It's powerful, versatile, unpredictable, brings a ton of momentum to any team, and it's pretty self sufficient. Right now I'm leaning towards keeping it OU, but it is still very earlier in testing, and I could easily change my mind. Nevertheless, I hope people take this post into consideration when choosing to ban Genesect, because I'd hate to it go simply because it can run a multitude of sets. Let's focus more on the sets themselves, and how they influence the metagame, in either a good or bad way, not how Genesect can run a million of them.