Since I fully expect Larian to fix the Dust Devil Skillbook sometime in the future (eventually), I'm going down the route of adding a Skillbook entry to the existing Dust Devil skill. That being said, this route may have unintended side effects (like Skills getting mixed up in their effects); I didn't see this in my test run with this new version of the mod, but it's happened to others before when the SkillData entries were overwritten.
New version with a Dust Devil Skillbook added in is here-
http://www.mediafire.com/download/ecs0nvybyc2lkwt/PurchasableSkillbooksV2.zipI also noticed in my test run that Phoenix Dive appeared at Aureus for my Level 2 party, so I'm probably mistaken about the minimum level thing to some degree.