11 people over 4 years doesn't seem like that much. Its not clear to me how big a population that is out of but if its government scientists i assume there are tens of thousands of those if not hundreds of thousands.

Still, FBI should be investigating every suspicious death of people with high level clearence.

Statistically, I would look at deaths from that age group among space flight science and compare this "blip" to the p50. I don't think it's easy to say if 11 deaths/disappearances over 4 years is high or not, without looking at the problem this way.