Skarmory is superior to Mandibuzz for the most part. It isn't weak to SR, it can also Taunt and Defog, and it can set its own rocks. While Mandibuzz can "check" a lot of Pokemon, checking is almost worthless for a stall team which needs to keep its walls alive to win. Mandibuzz does not counter as many threats as Skarmory due to its much inferior typing and SR weakness. Zapdos does not deal with Flying spam. If you are using a specially defense set, which I assume you are if you are using it to counter Aegislash, it is 2HKOed by Talonflame's Flare Blitz and can be 2HKOed by Mega Pinsir after SR. Staraptor murders it with Double Edge too. Everything else you listed is just checked by Zapdos, so a stall team will still have to find counters to all of those threats anyway, but now you have only 5 teamslots to do that with since you are devoting one primarily for stopping Aegislash.
SpD Gliscor is not that useful outside of countering Aegislash and Landorus, which may also be suspected at some point (and it isn't that great at countering Landorus if it hasn't activated Toxic Orb because of Knock Off). By running a specially defensive spread on Gliscor, you lose the ability to wall a ton of physical threats which can be walled with by a defensive variant. Specially defensive Amoongus is not very good outside of dealing with Aegislash and Keldeo. It could counter Thundurus if it weren't forced to run Foul Play instead of Sludge Bomb in order to deal with Aegislash.
Stall Pokemon designed to counter Aegislash may be able to counter a small number of other offensive threats, but in case you haven't noticed, there are a lot of offensive threats this generation, so dedicating one teamslot to counter Aegislash and a handful of other threats makes it very difficult for stall to succeed this generation. And I haven't even talked about SubToxic Aegislash. If you want to deal with that, you likely have to devote another teamslot for that. A Pokemon which can force multiple changes on stall teams while still being extremely good against offensive teams is absolutely unhealthy for the meta.
Who talked about a SpD set on Zapdos? Its best set is physically defensive, which can also check Aegislash as it avoids the 2HKO from Shadow Ball after Lefties and can threaten Aegislash with Heat Wave. Yeah, it's not a very good check, but it can scout for Aegi's moveslot and tangle with it a bit.
Have you ever used Mandibuzz? Because, from what you say, you fail to recognize Mandibuzz's biggest assets, which are lack of Fire weakness and thus the ability to deal with one of the most important threats in OU, Mega Charizard X, great special bulk (hi Landorus, Mega Venusaur, Latios, Latias, etc), and Foul Play, which allows it to deal damage back without having to depend on the unreliable Counter. And i never talked about Mandibuzz being used on stall, i was just talking about Mandibuzz as a Pokemon in general.
And Gliscor is not that useful outside of countering Aegislash and Landorus? What about Gengar then, one of the most popular and annoying stallbreakers for stall? Or CM Magic Guard Clefable, another problematic Pokemon for stall teams? Or what about AV Torn-T, also a very annoying Pokemon for stall teams to face, due to the combination of Knock Off, U-turn, and the ability to threaten most MEvos with either Hurricane or Heat Wave? So yes, outside of dealing with Landorus and Gengar, two of stall's biggest problems, and Torn-T and CM Clefable, two very real threat to stall, Gliscor is useless. And Quagsire, outside of dealing with Mega Charizard X, Bisharp, and BD Azumarill is mostly useless. But things don't work like that. SpD Gliscor can take on some of the biggest threats to stall, and this is what makes it a great set. Yeah Aegislash is one of them, but far from the only one. Landorus getting suspected is not relevant to the discussion we are having right now, because it's just an assumption. So, let's not base our discussion around assumptions and try to base them on facts. Gliscor does a ton of things for stall teams, and would be used even without Aegislash in the metagame. Instead of picking very viable sets and try to prove they are only used to deal with Aegislash (SpD Gliscor and Mandibuzz), which is a futile endeavor (every good players knows this is not the case) and a shitty argument, try to focus on other arguments with more substance to convince others that Aegislash is broken, such as a negative effect in the metagame or individual brokeness.
You are accusing us of doing everything to make Aegislash seem not broken, but how can you say this when you just called Mandibuzz and SpD Gliscor situational Pokemon that are mostly used because of Aegislash (especially when Mandibuzz loses to 3/4 of Aegi's sets, lol)? This is desperate, simply put.