So you're running Gliscor Zapdos Mr. Mime Smeargle Sylveon Espeon Vaporeon and Scolipede? Sure Gliscor can be used, but then you are weak to a whole new set of problems lol. Here we are discussing the use of Mr. Mime over Zapdos/Gliscor. If you do this, you lose to Mega Pinsir and Talonflame
Gliscor can fit over Zapdos well enough - it doesn't perfectly wall Talonflame or Mega Pinsir, but they can't 2HKO it once it's poisoned (Pinsir needs Adamant or Thrash to do so, Talonflame just cries), and it gives your strategy of Volt-turn + Talonflame plenty of issues on its own.
Here, let's assume you're in a battle - Magnezone / U-turner / Talonflame / three more Pokemon (including one Dark-type) vs. Scolipede / Sylveon / Espeon / Vaporeon / Smeargle / Gliscor. You get a strong lead matchup on him - Talonflame vs. Scolipede.
Seeing that Scolipede isn't winning that matchup, he sacks Sylveon - the Pokemon that is going to do the least to your team, most likely.
He then brings in Smeargle, takes a Brave Bird and Spores (or Spores the switchin if you opt to do that).
You bring in Magnezone and he goes to Gliscor on the Baton Pass, activating Poison Heal.
From here he can Sub against Magnezone, scouting your move or your switch, and acts accordingly - if you attack Gliscor with Magnezone (assuming you're running Specs, the only viable Magnezone set since last generation), he can Baton Pass to Vaporeon and get off an Acid Armor before passing to Scolipede. What happens when he passes to Scolipede?
252+ Atk Choice Band Talonflame Brave Bird vs.
+2 252 HP / 0 Def Scolipede: 260-308
(80.2 - 95%)
That.
"But Arcticblast, I would have gone to Talonflame on the switch instead of Magnezone!" Right - he has the switch initiative with Baton Pass and can go to something entirely different. There are so many ways that Flyspam Volt-turn vs. Baton Pass can go and some of them will inevitably end in the BP user's favor. I outlined one.
Discounting niche sets like Haze Quagsire and Roar Mega Gyarados, nothing - I repeat, nothing - is guaranteed a win against Baton Pass.