High damage Fwooshhhhhhhhhhhhh! As you can see, Flames of Ignaffar crit-ticking for 388546 damage. That’s freaking huge for FoI, and with 200% casting speed, that’s a potential (but highly unlikely) damage of up to 2,331,276 single target damage per second. But of course, this is not a single target skill. It also has 20% lifesteal on it, so you know FoiBoi brings the self heals
This build is not highly optimized, I came up with a concept, and these are the stats from the first play through of it, solo with crucible buffs. Without crucible buffs, the build is a little squishy… but the damage and lifesteal that it brings, it really is quite a powerful build.
The damage is achieved by double-stacking Total Damage %, and some tasty tasty crit damage to it. The Conduit of Runic Whispers adds a nice +18% total damage to the skill, but the Tainted Flame skill transmuter overrides the necklaces’ damage conversions, and also gives +15% total damage modified to it. As this damage is added multiplicatively, this gives a nice 35% damage boost to the skill. Awwww baby. This video demonstrates the damage of the build. Skip to 2:05 to see the fight with Mad Queen, where I manage to take her out by means of FWOSSHHHHHHH to the face before she can fire her PEWPEWSpikes back at mine. Once the damage starts pouring out, it seems to take about ~2s to kill her.
… I mean look at this damage on poor Commander Lucius just after Mad Queen. Ticks of 388,536 + 348,684 + 270177 + 99092 and whatever else is going. About 1.4m damage in half a second. Nice. Once the FoI faucet is open, the damage is big
I don’t think skill transmuter overrides conduit’s conversion. I think it’s gonna be split 50/50 between Conduit’s conversion and Transmuter’s conversion.
P.S. Side note: conduit in op’s build doesn’t have resist roll for some reason.
Sure, forgot the resist roll when built the char. But, the transmuter does override the item’s damage conversion. Transmuters take precedence over items. Here are some quick ingame screenies.
That has never been a case. We are doing some tests with modded items to reconfirm it, but transmuters and item mods have the same priority. Also your screenshots are not proving or disproving anything.
I think you can check the tooltip with a different conduit, like weapon damage to foi one. And if it shows much higher Vitality damage roll (because this time 100% of Lightning is converted to Vitality, not 50%) then you gonna see that it’s 50/50 between an item mod and a Transmuter.
EDIT: So here, couple of screenshots courtesy of @MergosWetNurse
Here is the FoI tooltip with the Aether FoI conduit
I suspect that just going for something like your setup with the Essence of Grim Dawn and then no transmuter is better. Like you convert all of the fire and then 60% of Elemental (Lightning) globally, no need to take transmuter give up Lightning to Vitality.
Or for a bit more tankiness and more aoe you can choose Chaos WoP conduit (but you gotta pump Word of Agony and of course Death Sentence). I would test different amulet options here (without transmuter).
Heh, this morning I sat down and did some quick maths to get a feel for it. You’re right in that using Essence of Grim Dawn with no other significant changes is better. A quick calculation shows that a “single, max non-crit tick with full RR up on a target who presumably has 0% chaos/vita resistance” shows about 3.5k difference in damage between the two, with Essence of Grim Dawn taking the lead.
Interestingly, if I take away Essence of the Grim Dawn’s flat chaos damage bonus to Flames of Ignaffar, then using the aether conduit comes out on top…
So, despite the 50% of lightning/fire disappearing to Aether, the mulciplicative +18% total damage from the conduit is still a very attractive option, even though clearly not quite optimal (and doesn’t provide some of the other benefits of Essence of the Grim Dawn - more healing, less skill cost, slightly more crit damage, and slightly more overall Chaos %)
As you can see, Flames of Ignaffar crit-ticking for 388546 damage. That’s freaking huge for FoI, and with 200% casting speed, that’s a potential (but highly unlikely) damage of up to 2,331,276 single target damage per second. But of course, this is not a single target skill. It also has 20% lifesteal on it, so you know FoiBoi brings the self heals 
