I fear that banning Aegislash will be like banning Lax in GSC. People lose their auto-check to most things, a role I find somewhat necessary in such an offensive metagame. Without Aegislash, far too many dumb sweepers/cleaners/wallbreakers/whatever can run through, and the meta would just end up as uncreative and it can mostly be explained in these three simple steps:
1. Sac something
2. Kill something
3. Repeat
My theorycrafting might be wrong, but from what I've seen on the suspect ladder, it isn't.
Then again, I literally don't give a ♥♥♥♥. I gave up XY OU a long time ago, and the only reason I'd ever play it again is for Tour/WCoP.
Not to go too off-topic here, but I think a major problem is how slow the tiering process is. I wish it was more efficient so other broken mons could get tests and banned. A ton of people have brought up how Aeg is the glue Pokemon of the metagame, but it's just barely checking all of the broken Pokemon running around in OU. I guess my counterpoint is that I wonder how much of a difference it makes. The metagame is largely what you've described with Aegislash.
So maybe it's the attackers themselves that are the problem?
*Landorus-I has Sheer Force and LO boosts that give it insane power while it somehow avoids being choice-locked or pounded by residual damage. It has Knock Off and Calm Mind to add insult to injury and murders stall. Offense has to revenge kill. Doesn't sound broken to me!
*Mega Charizard X is incredibly difficult to reliably check for any team not running Unaware Quagsire/Clefable and can nab free set-up because of the 50/50 it creates because of Zard Y. Oh yeah, Talon is the only Poke with priority that hurts it and it's immune to burn. Awesome!
*Mega Mawile has an effective base 259 base Attack and has STAB on a really good offensive type (Fairy), power priority that creates even more 50/50s, and decent coverage options that allow it to choose its checks. Great!
*Mega Pinsir has high base power moves, strong priority, Swords Dance, and really good Speed. It has "checks" that all need to be healthy or it just smashes you, and if its user keeps SR off the field, you're pretty much screwed. And this is our A+ rank mega. Cool!
*Talonflame is low key awful, people complain about Thundurus priority Thunder Wave but this guy has priority
Brave Bird for heaven's sake, can RK, sweep, Roost off SR damage, cripple checks with burn, abuse U-turn, and just generally be the worst thing ever. Yeah!
*Aegislash has been discussed to death but let's just say that you better have a bulky switch-in and a really freaking strong super-effective move that doesn't get neutered by KS or you might be in some trouble!!!!! Glad he's here!
*Mega Gyarados gets to choose its defensive typing to set up on whatever it wants and abuses everything with Mold Breaker and incredible power, bulk, and Speed. Waterfall even has a flinch chance! I'm also glad he's here!
*Thundurus has Prankster Taunt, Thunder Wave, and weather, and oh yeah, it sits at a 111 Speed tier with access to Nasty Plot and a ton of different options to break down checks (Superpower, Psychic, HP Fly, Knock Off, still Thunder Wave). At least Stealth Rock helps with it!
*Bisharp creates a ton of Sucker Punch 50/50s, can abuse Knock Off, has an amazing offensive ability, and has useful resists to get in on a bunch of stuff. It also destroys the only good offensive Defoggers in OU, because heaven forbid insanely overpowered sweepers be stripped of free hazard damage!
*Keldeo has Specs Scald coming off of 129 base SAtk and the best anti-Chansey special attack there is. Even better, it has decent bulk, some good resists, and can even serve as a wincon because it's so fast and Hydro Pump hits so damn hard. Woo Scald!
I could keep going, but these are the main culprits. I'm not saying ban them all, but I am absolutely suggesting that OU has a glut is VERY good attackers that makes the metagame top-heavy. Some above are broken, some aren't, but if Aeg is the dam holding back broken Pokemon running amok, I wish we'd just ban them. Because seriously, something with Belly Drum and STAB priority is like the fourteenth most threatening thing in the tier. I mean seriously.
/rant
(take w/ a grain of salt lol)