Looking at the released readings, I think that there is some evidence that the corruption of the Heralds is actually related to Cultivation.
First, in Jasnah's prologue
We believe this is either from Nalan or his partner. At first glance, this might be about Shallash. However, the implication that they are getting worse as a result of this woman getting worse.
Second, in Lift's interlude:
Because Honor declares himself the Almighty in the visions, we have often assumed that they are of Honor. But perhaps they are of both Honor and Cultivation, and as she pulls away they become more corrupted.