Here, unzip this to your x:\Users\[username]\Documents\My Games\LegendaryHeroes\Mods folder and enable mods in the game. That way if they don't fix it in the next patch, you'll still have it right (unless they meant to double damage and forgot to update the description, in which case you'll have it wrong and should delete the file).
http://darkseam.com/fe/FlameDartFix.zip
I haven't tested the file yet, but it should work.
