I was under the impression that DFAO should be able to completely darken obscured areas despite there being a dynamic skylight in the scene (which is global, i.e. shines in caves just as much as on the surface). Unfortunately, this isn’t happening, and completely enclosed rooms still get the skylight, despite DFAO. Am I missing something?
Can we get some picture examples? Are you getting any AO from DFAO? How large is the room?
I dont think its clean for small enclosed rooms. They said more then once that usecase needs much more work.
DFAO isn’t supposed to be completely darken obscured areas. It’s medium range occlusion. SSAO and material AO is short range, DFAO is mid range and lightmass baked occlusion is basically what you want.
Literally 6 boxes enclosing an empty space completely + skylight. The inside is lit. There is DFAO around the edges but it isn’t darkening the overall room one bit.
Have you tried increasing Occlusion Max Distance in Skylight properties?
Yeah, after a far enough threshold I just get blobby splatches of black on my walls.
This is correct
Note - ambient occlusion in the name means it has limited occlusion distance, as opposed to sky occlusion which does not, and only Lightmass can provide.
Unfortunately I use dynamic lighting only so no dice for me. 
So there is no dynamic solution for “lightmass baked occlusion”? I only use dynamic lighting in my game.