Okay, here are the shocking accomodations of my 19 dwarves.
In case you wonder: that's a "dining room" of 5x5, dug out of raw soil, with shabby furniture. The little office next to it belongs to the bookkeeper. The "dormitory" is a bed placed right in the middle of the main entrance. There is a dwarf sleeping in the dirt next to it, indicating the extension of this "dormitory".
The 1x1 meeting zone happens to be off screen, and it's outside. They often get caught in the rain.
Now, some of you might exclaim "tantrum time!!!" at the sight of this, but a quick glance at the happiness levels of the little suckers in Dwarf Therapist tells me the following:
Migration Wave #1
Lowest: 1479 points (ecstatic)
Highest: 2460 points (ecstatic)
Migration Wave #2 (only 1 dwarf remained from
Lowest and Highest: 2939 points (ecstatic)
Wave #3
Lowest: 1070 points (ecstatic)
Highest: 2952 points (ecstatic)
Children:
Lowest: 423 points (ecstatic)
Highest: 2070 points (ecstatic)
The low ecstasy of that child is because it happens to have been out of the baby stage for only a couple of weeks. Babies become content or even unhappy during that first year of booze withdrawal and lack of social contacts.
This amount of happiness points can't be thrown into a tantrum spiral, not even if you get half of the little pests assassinated.
If you start to hand them little individual rooms, they'll prefer to idle in these, abandoning their social activities, and thus getting much less happy points.
And if I on the other hand can be bothered to give them a good dining room and a somewhat more decent dormitory, then I guess I could also just leave the corpses of their assassinated friends lie around and have them witness the decay of their friends. Without having tantrum spirals.
Right now, they think that they are dining in a "pretty decent dining room", by the way.
I have an excuse for these shocking accomodations in year 4 of this fortress, by the way. I've been busy with that 5 z-level deep conglomerate aquifer.