Even by the metric of 'they're old' it is unlikely that this many would die pretty much right on top of each other, they would be more spaced out with some lasting years longer but it seams like there is someone big and famous dying every week now.....
Now if they were simply starting at that side of the age spectrum when it came to deaths(executions) that they made public, things could start getting really interesting reall soon.....
That isn't true. Even the internet can track deaths, even if they do obfuscate drug overdoses. A couple/few years back checked from 1996 to 2016, granted it was all hollywood types, not just comedians. An average of 1-2 a month is not uncommon. Of course a-listers aren't as common, because there aren't that many.
Also matters what you consider famous. Phil Hartman was a comedian, but also a TV and movie star.