Got reqs. Here are some thoughts:
(Disclaimer: I've only used a stall team so far in the suspect test, so my perspective is admittedly a bit limited. I'm going to ladder on an alt with a more offensive team in the next few days.)
Aegislash can be checked by a sizable number of Pokemon, many of which are fairly common in the metagame.
Consequently, most good teams will already be able to deal with Aegislash. Some teams will need to be adjusted, but there are many ways to account for Aegislash -- it is not "overcentralizing".
- For example, Swords Dance Aegislash is countered by Mandibuzz, Gliscor, Hippowdon, Unaware Clefable and Unaware Quagsire, all of which can switch in (even after a boost) and beat it 1v1. SD Aegislash can also be revenge-killed by many offensive pokemon in the tier, such as Bisharp, Heatran, Garchomp, Landorus-T, Tyranitar, Diggersby, etc.
- Life Orb Aegislash is harder to directly counter, but Mandibuzz still works, as do Mega Sableye, defensive Manaphy, and a few other things depending on its set. (For example, Sylveon can beat it if it doesn't have Flash Cannon, and Heatran/Bisharp/Chansey can counter it if it doesn't have Sacred Sword.) The LO set wears itself down quickly, and consequently it's much easier to revenge-kill. (The same revenge-killers above also work on the Life Orb set. Several other things can do enough damage to take it out when it's at low health, which will occur more often due to the recoil.)
- It's not really that difficult to figure out which set Aegislash is running. For example, you can tell whether it has Leftovers as it switches into damage or rocks.
I'm open to other peoples' arguments, but right now I'm strongly leaning to unban Aegislash.
- If you have a stall team, you might just be able to counter it. If you have an offensive team, you might not be able to switch in directly, but at worst you'll be able to revenge-kill it (or put pressure on anything that decides to switch in). Also, an offensive Aegislash set might have trouble switching into an offensive team in the first place.
- Many other OU threats (Landorus, Mega Scizor, Mega Gyarados, Mega Charizard X, etc.) require much more preparation in teambuilding than Aegislash does. As a wallbreaker, something like Landorus is generally more of a concern than Aegislash -- it has STAB Earth Power and Sheer Force. As a bulky sweeper, Mega Scizor is largely more threatening for its access to Roost and Technician Bullet Punch.
- This is not to say that Aegislash is outclassed -- it has its advantages over the above threats. However, it does not put any more pressure on teambuilding than the above threats.
Aegislash has a number of checks without a doubt. However, Aegislash is fully capable of getting around whatever checks its teammates want removed. It was always known that Aegislash had a lot of checks, but almost of them were broken down by a varying Aegislash set.