I'm very interested in learning more about the Rune Lords. As I think I will be able to adapt them to a campaign I was working on a few years ago.
In a home brew campaign I started to run I had a very similar design for rulers. They also, purely by chance where called Rune Lords. They rose to power after a ingenius wizard made copies of what was called the Goddess Rune. It was a rune created by the planes creator, she had a mortal avatar that she blessed with the Goddess Rune. During an all out war between Dragons and pretty much every other race that did not have draconic ties the Rune was lost. Only to be found by an arch magi who attempted to duplicate it. During the Dragon Campaign, as the dragons began to lose ground they threw up a power shield encompassing half of the entire world to seperate themselves from the other races. The magi was attempting to duplicate the Goddess Rune to hopefully use it himself, since he could not wield the original himself. When he tried he was not able to duplicate it in full effect and no rune was powerful enough to encompass more then aspect of the original. I broke the runes down into each of the base ability scores, basically one powerful rune for each stat. Eventually the Arch Magi gave those runes to his greatest minions, each of them empowered by the runes.
So basically a similar but much less indepth story. I very much like the fact that each of the Rune Lords that the Pathfinder series will be using also distinctly seperates them using the 7 Sins, since it gives them a bit of their own personality.
I look forward to seeing how these 7 Rulers develop, aswell as the Pathfinder AP as a whole! Keep up the great work!