Dark Harvest and Dying
If you die, you do not receive soul essence for your takedowns.
That's pretty silly, especially for the jungler who gives up time to gank in the hope of receiving stacks, but dying prevents it.
Obviously no one tries to die during ganks, but if your corpse is nearby you should still obtain it if you killed them.
Out side of lane phase its much more punishing, if you die early in a team fight but still contribute significantly, you miss out on 9 possible soul essences..
Taking DH rune is a risk. It shouldn't be almost impossible to catch up on because of a stupid interaction with death.