King's Shield is one of the better moves Aegislash has. If you can predict your opponent is going to attack you with a contact move, you can decrease their Attack, which means you can take more hits. That, in turn, means you have more time to set up. Then there are the more trickier Autotomize sets that don't utilize King's Shield, but I'm not too keen on those.
The thing with Aegislash is, you want to be slower than your opponent so you can tank hits while in shield form, then retaliate in sword form. You really don't want to be in sword form when your opponent attacks. For this reason Speed EVs can be detrimental. Bulk is in my opinion the better alternative, so invest in HP and in your case Attack. I don't think you have Shadow Ball or Flash Cannon (nor Weakness Policy) so mixed set isn't going to work all that well.
I'd suggest you run King's Shield, Swords Dance, Shadow Sneak/Claw and Sacred Sword. Not only you have good enough coverage, but also Swords Dance for setting up and King's Shield for protecting yourself and changing back to shield form.