Heralds and increased spell damage nodes

From wiki:

"Casting and Spell interactions

Because Herald of Thunder is a Cast and not a Spell it does not receive any direct Spell bonuses from Gear, Skill-Gems or from the Skill-tree. This also applies to support gems which specifically modify Spells (Eg. Spell Echo and Iron Will). However when using a Spell the additive on-hit damage will receive indirect bonuses from Spell modifiers."

So increased spell damage increases some part of Herald of Ice and Thunder if not the whole lot?

Under Herald it lists 3 different damage modifiers one general, one for spells, one for attacks. Do the spell damage nodes then increase the one listed for spells?

Or is it a case of the damage for spells added onto the spell you're casting (in my case incinerate) then getting buffed by the spell damage node?

I guess my goal is to figure out if it would be better to get the faster casting nodes at the start of witch for my incinerator or leave the spell damage nodes? I'm running AA, LW and Molten Shell in addition to Herald of Ice and Thunder in addition to Haste (which I may swap out if I find a gem that works better - perhaps discipline/grace etc). Spell damage nodes would add to Molten Shell but that's about it...

Simply CastSpeed as long as using Incinerate. More Casts per Second more Casts gets BonusDam from Heralds.

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Mishraehl wrote:

Or is it a case of the damage for spells added onto the spell you're casting (in my case incinerate) then getting buffed by the spell damage node?

Yes.