It is helpful to mention, that the combat art modifier, Combat art range +X%, works great with Blazing Tempest. However, with Incendiary Shower the boulders are spread out and the effectiveness is reduced. When killing bosses, it is always best to focus the boulders into a small area, thereby eliminating the target quickly.
Conversely, Blazing Tempest works very well with an increase of range. It makes it a trifle problematic, the conflict between these two Combat Arts.