Yayyyy Valk’s finally posted his healing potency formula. Below is an excerpt and link to his new blog.
Hello FFXIV players, this past weekend my time was limited, but I did have the chance to look into the healing mechanics of the game. Not surprisingly, they were remarkably similar to the damage mechanics. All testing on my part was done with Thaumaturge. Here is what I found out: http://valk.dancing-mad.com/?p=53