Introversion

So I have 150 workers and I clone a dorm. There's floors, walls, and at least 30 objects to be placed....but ONE workman at a time comes to build this dorm. I cloned something like 15 more and maybe 30 came to build, the others just screwing around near the gates at the edge of the map.

So I set it to priority. Suddenly everyone is working. What's with this? So frustrating because when you set priority they all drop things and I have to double check they've built pipes etc.