Belated thought: Given just how appropriate it is on a deep level that Dhar should cause a shift to the minor key that I have to wonder how much a part Dhar Insight ended up playing into that at all.
Because thinking over the mechanics of how Dhar works, and how the minor key works, It feels like something so elegant that it either came out of the most basic level of understanding, or was the work of a master.
It'd be funny if there was a little rabbithole where every person who looks at a Portentive Organ is struck by it's workings proportional to how much they know.
So the average wizard wonders "Hunh, how did they make the Dhar detection work. Oh, neat."
The average dark mage is going "Wait, no, how did they make the Dhar detection work?"
And the actual old vampire, very experienced necromancer, or other master dark mage with the inclination to study one is thinking "Oh, this person gets it. Why the hell would a proper dark mage work on a project like that?"