I found crystal formations at both of these locations on Sanctum of the Exalted (I don't think many people are looking for them here, I've only seen one on the GTN). After I picked them up, I soloed Ulgo Siegebreaker to see if I could get a schematic, but he didn't drop one, so I can't confirm that he drops these. I'm now testing the 2 hour respawn on the crystals and I will continue downing the Siegebreaker to see if he drops a schematic.