The pyromaniac trait doesn’t activate more than once for spells that cast multiple times, either from the Echo perk, Multicast buff, or just for spells that have the cast an additional time property, or spells that naturally cast multiple times as part of their effects. It will trigger when a different spell is cast though.
I’m not sure if this is a bug or intended behavior, but it seems like it should activate each time a spell is ‘cast’ by one of your creatures. If intended, maybe add a line that says it will not activate for repeated spells?
It does seem like it could get a bit broken if it did work for each repeated spell.
Edit: This is in version 0.0.14