It would be nice if there was a config option to change how common Draconium Ore is found.

At the request of the FTB Team iam going to be adding an option to disable ore gen so that it can be controlled using cofh.

Will that include full manipulation of spawn rates, or just disabling it?

Just disabling it but cofh has the ability to to spawn ores from any mod and it has very good controll over where and how it spawns. So you will be able to disable DE ore spawn and have cofh handle the spawning of draconium ore... Assuming you use cofh.

Yeah, I'm using CoFH for all my other world generation as well :)

Config option to disable ore generation has been added in snapshot 4