Have skilled Earthscorcherer in Warpath three, so it now has fire scaling tag on it.
The test. The only ignite chance comes from passive tree alongside the path to Earthscorcherer (10%). Then Calamity unique helmet is equipped, which says “150% chance to ignite with fire skills.”
Expectation: Target dummy gets ignited with every hit, as chance to ignite should be over 100%
Reality: Ignite chance from helmet is not applied (real ignite chance is about 10% from the skill tree). Despite the Fire tag Warpath is not considered a fire skill.
I assume this is a bug, because Elemental Nova works fine. It doesn’t have Fire tag initially, so with 0% ignite chance and with equipped Calamity dummy is never ignited. Skilling Fire Nova adds Fire tag, and then Elemental Nova always ignites (even if non-fire nova is chosen).