Does a Wands spell necrotic damage stack with the % health converted when you directly cast a necrotic spell , I’m wondering what counts as a necrotic spell.
Aka I’m a runemaster say I use frost claw but I’m using a wand that has spell necrotic damage would that allow me to gain the additional effect of twisted heart?
So I get the bonus from elemental damage as well as necrotic spell effects even though I’m using a wand with necrotic spell damage versus a skill/spell with it?
The spell you use, would need to have either the necrotic or elemental tag. Just having %necro damage or even flat damage does not make a spell ‘necrotic.’
very useful to actually know /be verified was gonna switch to a necrotic wand to try and double dip …lol 
The flat added damage from certain items or passives is irrelevant. Any skills or procs or anything that requires a specific skill type (eg, fire skills, necrotic skills, whatever) is based on the tags, not whether any flat damage of the appropriate type is added.
So if you’re using a skill with the void tag (eg, Smite converted to void) & are adding some elemental or necrotic flat damage (either from a Profane Wand for necrotic, Mourningfrost Boots for cold or a Coral Wand for lightning) to the skill then that’s not going to proc the Twisted Heart effect since the void-converted Smite has the Void tag not an elemental or necrotic tag.
No, it won’t.
Chaos Bolts, Ghostflame & Chthonic Rift all have both necrotic & fire tags by default so they would work as long as they aren’t converted out of both necrotic & an elemental tag.
Great tips thanks !