Holy fire / Burning damage with RF

Hey,

So I've recently made a RF ES based build. Up until now I've not touched Holy Fire, (The 40% increased burning damage in the Templar area), the reason for this is I wanted to be more tanky and so I've picked ES nodes instead. However, I've now tried picking up the Holy Fire node along with the small burning nodes on the way to it, which should increase my burning damage by 70%. Comparing my damage dealt to Vaal in The Apex of Sacrifice it doesn't seem it gives any significant increase of my damage, frankly it doesn't seem to change it at all? Unalocating the burning nodes and trying to kill Vaal gets him down to about 25-30% hp before he is going down and the same happens when I have the nodes allocated. Have I missed something in a patch or is Holy Fire + RF no longer valid?

Thanks in advance,
A confused casual player.

Perhaps you already have a lot of increased burning/fire damage, so the 70% increased damage isn't very noticable?

The only burning increase I have is Increased burning support gem 20/20. The only fire damage I have is Explosive Impact which gives me a total of 55% increased fire damage. Besides that I don't have any fire / burning damage. My RF is linked to Increased Area + Increased Burning + RF + Elemental Focus. Picking up the Holy Fire should at least show some result on the vaal hp on the way to Atziri imo. So it seems quite weird imo.

Ah I see, then it's more understandable.