I'd love to see a statistical analysis of whistleblower deaths on the US over the last 15 years. I'd be extremely susprised if it wasn't enormously anomalous.
It’d be hard to draw any conclusion. A whistleblower must be under extreme stress and pressure which in itself in some way or other will increase the risk of death — so that has to be taken account before saying the plausible cause for the excess deaths is assassination.