It seems that either the goblin civ or pathing onto my embark is terminally bugged. I received _five_ visits, all listed as "siege", and each of them was nothing but a pitiful six-to-seven-gobbo ranged squad, of which one or two _always_ got stuck at the map border and completely failed to move.
Actually, at the moment of loading the forces onto the map, i saw an axegoblin, but that one apparently instantly left again.
The massive goblin thumper worked perfectly, but it's just stupid to never get anything but that completely irrelevant scout squad to play with. What's the point? Anyway, it took out all five goblins that were capable of moving at all, and one mason who decided to "clean" and ate magma.
I'd really like a way to designate a "for the love of all that's holy, this area is utterly off-limits and you're not, not, not, not, not allowed to "clean" here, you insane morons" area (and yes, it should have the full description, the insistence on cleaning areas while they are super mega fatal to enter is infuriating). On a less suicidal but even more irritating note, they went onto a neverending vomit conga to clean/re-paint a few tiles under an overhang that could only be reached by long-range aboveground travel; i had to order the place channelled open to stop the idiocy.
Oh, and the last known forgotten beast wouldn't spit its webs through fortifications. So we dropped a floor on it.