Sunshine,
Right, your advise jibes with the most recent germing/growing instructions I've come across. I've been told to scatter the seeds on the surface of a sand/perlite mix, and to just barely cover them with a coarse sand. They may need light to germinate, as you've rightly pointed out. And that they love high humidity when they're young, which frankly surprises me. I would've guessed the opposite. Damping off, as the name suggests, seems to be encouraged by moister conditions, and these little guys succumb to it like a hypochondriac at a bus-station sushi bar.
One thing that everyone seems to agree on is that they're tricky to grow, so congratulations on your success!
I wonder what their natural growing conditions are when the seeds germinate in the wild. Is there some sort of 'monsoon' condition that triggers germination? I gotta get on the Google-train and do some more research.
Of all of the batches of B. sacra seeds I've encountered, I'd peg my germination rates at 10%, and no higher. If it's true that they lose their viability quickly (and I have no reason to doubt this bit o' common wisdom), this also seems to suggest to me that they must encounter some brief periods of rain, etc. to trigger germination; I'd hazard that a true, year-round desert species would produce seed that could remain dormant for many years without losing viability.
Do you also grow any Commiphoras?