Specifically for Breath of Fire, it states “When you hit an enemy with fireball while in a flame rush…”. How can you hit an enemy with a fireball while in a flame rush? Just shoot it before you flame rush or what?
Look at the node preceeding Breath of Fire.
“Casting fireball and then using flame rush in the same direction causes flame rush to deal more damage” - which has nothing to do with hitting them with a fireball while in a flame rush, unless you mean that it implies you have to hit them with flame rush before the fireball you shot hits for Breath of Fire to proc (which was the original question)? Seems unlikely given how fast both skill fly.
No, the node before is trying to get you to use Fireball then Flame Rush immediately afterwards.
Is a fair point.