At the same time though Espeon is not inherently broken, just the combination of BP+Magic Mirror. I can understand your argument and honostly I agree with you. By that same logic if we ban Baton Pass we're literally banning a playstyle which rips weather arguments a new one. But it's Espeon without a shadow of doubt is not broken. Only the combination of BP and Magic Mirror. We could complex ban but then we'd be hypocrites for Blaziken. We could ban Baton Pass but then we'd be hypocrites for not banning weather. We could ban Espeon but then we'd be hypocrites for banning something that's not inherently broken. In any situation we lose.
However, if I were to pick given your arguments influence then I'd have to agree with you. Espeon is the lesser of 3 evils.
My argument is that Espeon
is inherently broken, because we've been in a situation where Baton Pass has been without MM+BP, yet, it was not even close to being broken at that time.
It dosen't matter if something is only broken in one team archtype, and not in others. Manaphy was only broken on Rain teams. Did that stop him getting banned with a Supermajority? This further adds to the logic that Espeon should be the one to get banned.
Banning BP+MM is just an attempt to keep Espeon in the metagame, and thus, is something which shouldn't even be discussed. Banning that combination is basically saying we may as well ban Blaziken + Speed Boost, or Darkrai + Dark Void, because Espeon is the only pokemon with that combination.
Banning Baton Pass outright is also foolish, as without Espeon, it's not broken. It's a good-at-best tactic. It's a thousand times easier to handle when you can WW/Roar it out, or Taunt. Espeon prevents that and spits it right back at the user.
The only logical argument is that Espeon is the one who should be banned. We already have the precident with Manaphy, when it comes to banning something only broken under one playstyle, so why not Espeon?
That said, Baton Pass has always received a fair bit of hate from competitive circles for being a 'noob' tactic.
To be frank, I don't think banning moves should even be on the table, unless it's Acupressure, Double Team, Smokescreen, Flash or Minimise.
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I'd also love to hear the reasoning why some people thought Snow Warning is broken still... I see no logic behind that at all, unless people are afraid that Snow Cloak Froslass and Stallrein will dominate OU if Hail is the only weather.
Just curious, since this team archetype is apparently popular enough to be considered banworthy (>_>), what is the standard Baton Pass chain team?
Popularity has nothing to do with bans. Wobbuffett wasn't popular in Gen 4, but was banned. Deo-N hardly got any use at all, but was banned.
Although popularity of the checks to something, and the suspect itself can be an indicator, it is not always the fact that central forces are the only broken ones.