Perhaps "messenger" position could do a double duty as a postman, while in the fort and for communication with outside world when sent to different places? I agree that socialization needs to be improved.
You've set me to consider a "Messenger" role who is basically an "Information haulier". No physical items involved, their job (when fulfilling the generated tasks) is to travel between those wishing to communicate and those that they wish to communicate with (which might be a mutual thing, or not, but probably involves many such client-pairs). Either they have "spooky knowledge about who wants to chat" or they just try to visit everyone and modify their potential follow-up visit priorities according to who they now know has asked to be reminded to who.
Personality (pyschological qualities) might be useful for both being accepted as messenger and not minding carrying a bit of the 'mood' of a message (relaying a complaint to an administrator, echoing messages of affection to lovers). In addition to the various problems that messengers might have in reaching (or crossing the gap between) their disparate 'clientelle', they also need to potentially deal with reporting unfavourable opinions (as intermediary), evoking the times when the old classic phrase of "don't [shoot/crossbow/hammer/grapple/bite] the messenger" might be considered aposite.
And, under the "Villainy" aspect of hidden ulterior motives, it is quite conceivable that a secretly provocative messenger can
deliberately misconvey messages, I'm thinking, stirring up trouble/fomenting bad feelings. So there's a risk to a fort, as well as(/instead of) the one who is keeping everyone informed.
But it
can keep even tightly-controlled workers (held in place either physically/stuck-in-a-hole/wrong-side-of-fortifications or by burrowing/logistics) from getting upset thanks to zero social interactions, so long as they can be approached within conversational distance (if it needs to be shouted, the message counts for less).
(...and then that got me onto thinking also about Dabbawallas.
Personal 'food hauliers' (Dwarferoo/UberRoasts?!?), to deal with those who are hungry (and reachable!) whose job-poriority (or other need to be somewhere) is still slightly higher than their famishedness and tendecy to find the nearest actual food stockpike(+dining room). But that's probably a little less medieval than... you know... actual Messenger Dorfs.)