I've found the more I play that I am using Hereditary Rule hardly ever anymore. I guess the reasons must be that I get the Pyramids about 50% of my games then switch right into Representation, which I consider a more useful civic under most circumstances, early or late game.
I also was thinking that human players might not find it as useful because it requires keeping troops in the cities and we are typically using them for taking it to the enemy. And I don't need the happiness from troops early on, because I might have a couple really large cities that grew quickly, but mostly the other cities are smaller. So the happiness in 3 largest cities is good, plus resources, and whipping keeps the population down elsewhere for a while.
What are your thoughts and are there some good situations where this civic is better than, say, Representation? And is this civic basically worthless if you are using Slavery for most of a game?