Locked Doors, the enemies, and you.

This is partially tied into the way that enemy raids spawn into the game, as well as how you are notified of them. So could be a null issue is there is some more forewarning of enemy attacks, or they spawn farther away.

I built a base in bottom right corner of map, then proceeding to build a larger wall around the "castle".  Issue that is occurring is when enemy attack warning goes off, or even "my lord so and so is going to attack soon" enemies are spawning into the game at either instance RIGHT at the wall, with sometimes even spawning inside the wall perimeter.

This creates the odd situation that I have no time to send a minion out to the gates, lock the gates, and get them in position for the attack.  However if I leave gates prelocked, myself as well as allies cannot be through the gate.  

Having gates automatically "lock" against raiders might help, would also make enemies carry grappling hooks more interesting rather than it being more of a blessing as they don't have a bow.

Alternatively, make add a portcullis that is of higher cost than your standard wood and stone door that will actually repel enemies by allow yourself and allies to pass.  

Ramble/suggestion, but it certainly is odd having enemies just meander right through all your walls and gates without issue.