Ah okay flames and global in general makes total sense. As far as grimhildes with the 4 uniques I mentioned, since the witchfire applies from ignite/damned overload proliferation and from hits, would the ones from ignite/damned overload prolif have lower damage than the ones from ghostflame, due to the ghostflame applications having the additional chance from fire skills and channeling during calculation? I thought the node was just checking what the stat in your character sheet giving the damage boost all the time.
I haven't gone to double check so I could be wrong but from the wording you put, the above guidelines work. If it only cares about global, chance for fire skills isn't global.