I personally think Genesect should not be banned. The reasoning is quite simple, if it is banned stall becomes more prevalent, and I think thats harmful for the meta. Sure, banded U-turn hits hard, however I think Pokemon is its most fun when we have balanced/HO teams going at it. Furthermore, it is not broken like people claim, if you run scarf it becomes extremely hard to OHKO things, and if you choose the band route your getting out-speed by pretty much everything. Also, I think download works slightly like beast boost as in you can anticipate when a mon has lower def/spdef and choose the right time to send it out. Thats just what I like to call strategy, and if you feel uncomfortable dealing with that then I think thats not the pokemon's fault but your own.
In response to these
- Stall prevalence: This should not be what governs the ban. I'm not a Stall player, but it's better for us to aim for a competitive Stall meta post-Genesect than an unbalanced Offense Meta with Genesect (assuming of course either of these scenarios would be the case). We don't make current ban decisions based on a prospective future meta, only on whether the current meta benefits from the element's presence
- No one is expecting Genesect to do every job of all its sets in the same match, but the ability to reasonably bluff several of those sets which call for different counterplay is a massive constraint on team building and and ongoing burden that lays more heavily on Genesect's opponent than its user. No one is arguing that Genesect is broken, but he brings too great a disparity in risk-reward to be a fair element. And as a small addendum, while not a speed demon, Base 99 Speed is still acceptable for a mon with Genesect's power, Download, and access to Priority.
- Download is not comparable to Beast Boost in that manner. Download will activate immediately when Genesect enters the field, and besides favoring his options against the particular opponent, there's no condition attached to it. Beast Boost only activates in response to a KO, meaning that while it can snowball momentum, it's not particularly factoring into whether or not a UB generates it outright, Pheromosa. Furthermore, Beast Boost is derived from how the user is specced, and nothing else, effectively a semi-customizable Moxie. That said, it's going to be the same boost every single time it procs within a match, purely on the back of how the player built the UB. Genesect's Download boost is influenced in theory by two factors: When the user brings Genesect in, and what/if the opponent switches to before Genesect hits the field. Along that line, Genesect's Download is much more flexible aid to it, and the opponent can't fully control what boost they're going to be dealing with against Genesect, especially since the ability's premise is meant to favor whatever the opponent is weaker to in theory (even if this is obviously not how it always breaks down).
- "Thats just what I like to call strategy, and if you feel uncomfortable dealing with that then I think thats not the pokemon's fault but your own." As a closing note, this type of ad hominem and condescending does not help your case. If your argument is strong enough, it should be able to stand on its merits rather than undermine the opposite side with personal attacks.
With that (and as I have mentioned a couple of times before) - has it not crossed your mind the possibility of logic checking an opponents team preview? Examples being the possibility of HP Ground on teams that look like they would otherwise loose to Heatran/Magnezone or similar, The possibility of carrying Bug Buzz and/or Flamethrower alongside Manaphy / Azumarill and various other waters... hell, even Steelium Z on teams that look as though nothing else could be carrying a Z-move. Does that give you any ideas?
In the majority of cases, this can and should be the idea employed to counter play a versatile mon, but I don't think it's the most effective method with regards to Genesect, as several of Genesect's multiple sets can perform similarly enough to each other that they can bluff each other, if not almost substitute for each other at times.
Your later posted Scarfchomp example is a point, but part of why it works as such is because Scarfchomp's playstyle and role is very different from how LO or Tankchomp would play, so it's much harder to bluff it without outright playing it poorly, if the illusion is even possible in the first place. Genesect's Expert Belt, Z-move, and Scarf sets can be played much more similarly, such that the only surefire way to see what the set is would be for the move to change, Z-move to happen, or Genesect to outspeed something, and if the opponent is unveiling the identity of the set in such a manner, it's very likely they're in a position where they gain a sufficient advantage for doing so.
Besides this, Genesect's versatility and ability to lure for teams can go two ways. I posted a breakdown of an example earlier, essentially amounting to having Tapu Koko and Genesect one one team, alongside a strong Alolawak answer. The question then becomes if Genesect is another mon to support against Alolawak (via HP Ground) or be supported alongside Koko. These are two equally real possibilities that have to be considered by the Alolawak team, and they require very different counterplay that can be devastating should they guess wrong, whether directly via losing Alolawak (and thus being vulnerable to Koko cleaning) or over the course of a match from hesitating to use what could be their best Genesect check. I think that the duality of team synergy needs to be properly accounted for when trying to argue for or against Genesect's versatility and bluffing potential, as while I'm sure many players on both sides are aware, I think this point could stand to be bounced around a bit more.
I don't see how those two games support the idea of Genesect being broken.
In the first game, Dice simply did not play optimally against Genesect. You don't mess around setting up rocks with a Heatran (or Lando) on a Genesect without having any clue as to what it's running. If Dice had a mega Venusaur or Amoongus instead of Heatran, it would be a good play to just stay in and chill. If Dice had simply attacked it instead of going for the SR, the supposedly broken threat would have been gone.
I don't want to say you're wrong at all with this, but I would just like to play devil's advocate so that you can perhaps explain your stance a bit more clearly for my perspective. In this match up, both mons were the leads, so the match up is entirely based on what Genesect is running rather than later battle circumstances of when it was brought in. While HP Ground was the scenario that unfolded, another plausible scenario was a Scarf/EB Genesect that couldn't touch Heatran, and would use the first turn to U-Turn out (or hard switch, but the main thing is Genesect would leave before Heatran's action). ABR could logically go to his own Heatran or to Keldeo if he anticipated a Fire type move against the Genesect, so SR isn't an illogical choice since getting those Hazards up in those scenarios would probably do more good in the long run than firing off a nulled/resisted Fire move and potentially having to Switch Heatran out afterwards (without confirming if either Heatran might have EP or which would outspeed, or any number of factors affecting the mirror match up). The Heatran wasn't defensive, so it only even survived due to a roll
252 SpA Expert Belt Genesect Hidden Power Ground vs. 0 HP / 4 SpD Heatran: 283-336 (87.6 - 104%) -- 18.8% chance to OHKO
252 SpA Genesect Hidden Power Ground vs. 0 HP / 4 SpD Heatran: 236-280 (73 - 86.6%) -- guaranteed 2HKO after Leftovers recovery
252 SpA Expert Belt Genesect Hidden Power Ground vs. 252 HP / 4 SpD Heatran: 283-336 (73.3 - 87%) -- guaranteed 2HKO after Leftovers recovery
The only roll here that seems to immediately work for the turn 1 shown is EB Genesect vs Offensive Stallbreaker (if I'm mistaken, perhaps we could get the sets from the two battlers), as the other sets wouldn't break 90%. While a lower percentage, Heatran had a non-trivial chance to be OHKO'd from full by an HP Ground, and if he'd been KO'd, Dice's choice of response move wouldn't have mattered if it was a Fire type move.
My main thing being, it's very easy in hindsight to say that the Heatran's choice was poor play, but that's only because we saw the (then) unknown variable of HP Ground. There was an equally possible choice of action that would still put Dice at a disadvantage if the Genesect had indeed had a losing match up. For us who know the set, it's a suboptimal play, but in that particular moment, it appears as nothing more than a misprediction regarding what the Genesect would have. It's very easy to say what should have been done, hindsight being 20-20, but it doesn't strike me entirely as being objectively Dice's fault here.
I think it also fair to note, Genesect might be checked decently by Venusaur and Amoongus, but the same way HP Ground and Douse Drive emerged for things like Heatran and Alolawak, is there any reason he couldn't adopt a similar lure option if those became the most common response and it proved needed? Even then, standard Amoongus (no Thick Fat) only seems like it'd be a check if Genesect is scarfed and not running the very viable Ice Beam, and it doesn't even survive that without Max/Max+ for special bulk
+1 252 SpA Genesect Psychic vs. 248 HP / 144 SpD Venusaur-Mega: 212-250 (58.4 - 68.8%) -- guaranteed 2HKO after Stealth Rock
+1 4 Atk Genesect Zen Headbutt vs. 248 HP / 96+ Def Venusaur-Mega: 144-170 (39.6 - 46.8%) -- 35.2% chance to 2HKO after Stealth Rock
+1 252 SpA Genesect Ice Beam vs. 248 HP / 92 SpD Amoonguss: 300-354 (69.6 - 82.1%) -- guaranteed 2HKO after Stealth Rock and Black Sludge recovery
252 SpA Genesect Ice Beam vs. 248 HP / 252+ SpD Amoonguss: 156-184 (36.1 - 42.6%) -- guaranteed 3HKO after Stealth Rock and Black Sludge recovery
+1 4 Atk Genesect Zen Headbutt vs. 248 HP / 8 Def Amoonguss: 268-316 (62.1 - 73.3%) -- guaranteed 2HKO after Stealth Rock and Black Sludge recovery
If I'm not grasping at straws, this just goes back to a common criticism of Genesect: it's never without an option to subvert the meta's choice of answer(s) to it if need be.