I wasn't here when the quest was first used, and my city isn't telling me anything. Would the village start shouting on your ct or osmething if they attack?>

That'd be a good idea. At the moment the only way we know if there are undead orcs are when other citizens saw them or died to them on deathsight.

From what I can tell, there is some global message that announces the orcs are marching on (insert village name here). Not sure what is the exact message.

As far from true as possible. They are coming from those obelisks that you usually summon guards from, and the obelisks can be "closed" somehow to prevent it from happening.

EDIT: No, it doesn't give a global message. But the orcs are weak anyway.

I thought I've seen a bunch of orcs storming into angkrag before. Meh, just wait for the newbies to wander in Just like canaries. Send them in, if they stop whistling, something's in there

It does give a global message.

I just saw Estelbar being invaded from Glomdoring.