In the changelog Derek mentions that Clerics reduce unrest by 5% per essence. However when I hovered over Clerics in the build menu, it said they lower unrest by 10%.
I had two essence in the city. If the clerics did indeed take the essence in the account, and as such reducing unrest by 2*5%, the tooltip needs to say that it's related to essence. Otherwise players keep wondering why sometimes it gives more and sometimes less of a benefit.
If clerics always reduce unrest by 10%, the changelogs have a bug.