If my calculations are correct (it looks that way though), there are couple issues with Flame Burst node in Fireball tree:
abilityGrantedByNode for Flame Burst node refers to a different Flame Burst ability, not the one actually used, so you see wrong ability in ALT tooltip for this node. In fact Flame Burst is applied via AilmentID.FireballStackForExplosion which has different stats.
With my calculations it looks like Flame Burst uses intelligence scaling (the same as Fireball itself), because with the scaling DPS is exactly the same as displayed in Fireball DPS tooltip. I’m not sure whether it’s a bug that it scales or it’s a bug that this scaling is not shown in Flame Burst skill tooltip, perhaps the former.
Fireball’s Burst of Flame sub ability tooltip was indeed referencing the wrong ability, thanks! That’s been fixed internally.
Non-equippable triggered spells like these usually don’t have attribute scaling on them because they inherit the attribute scaling of the ability that triggered them. It’s definitely unclear, and something we’re interested in finding a clean solution for in the future.
It’s probably simplest (for the player) if the tags that affect the triggered spell/skill/whatever are stated as they are for the equipable skills, since that’s what the player is being trained to expect.