I ran some new tests to determine whether the Champion ascendancy damage reductions apply to the player when Warchief Totem taunts the target via Conqueror. To be more specific, I'm referring to these.
Conqueror
"
25% Chance to Taunt on Hit.
(Enemies you Taunt can only target you, and deal 10% less damage to anyone else.)
Worthy Foe
"
Enemies you Taunt deal 10% less Damage against other targets.
Do note that all of the following tests were done in 1v1 PvP duel with a friend of mine.
We ran three sets of tests where my friend would wield a Barbed Club and attack my character ten times. My friend was specced to Resolute Technique. I'd snap a screenshot between each hit. My character had specced out of all Life Regeneration. My passive tree was unchanged between the tests, except before the third when I allocated the node Worthy Foe.
First test was done without any totems active, to determine the base damage without any taunts.
Second was done with my totems up hitting my friend and Taunting him. He was making sure he had a Taunt debuff when hitting me.
Third was identical to the second gameplay wise, but I had Worthy Foe allocated.
Here are the results in a spreadsheet format extracted from the screenshots.
From these results, it seems clear that both the inherent 10% less Damage from the taunt itself, as well as the additional 10% less Damage from Worthy Foe, stack with each other and count the player as "anyone else" or "other target" as per the quotes in the descriptions above. In other words the game differentiates the player and the totem as two different entities where the totem is the one doing the taunting while the player receives the damage reduction bonuses.
Also perhaps a worth of note is that the Conqueror node line "6% reduced Damage taken if you've Taunted an Enemy Recently" does NOT seem to work for the player. It still might for the totem, but since the Life Regeneration portion does not work for either the player or the totem and they both use same wording, I highly doubt the reduction works either.
TL;DR:
Both damage reduction inherent to Taunt and a further damage reduction from the Champion ascendancy node Worthy Foe stack with each other and apply to the player when using the Warchief Totem to apply the taunt via Conqueror node.
