Doublebilly dropped a new wc barb build and casually mentions socketing a protectors jewel in your merc increases the players physical lower resist as well. Anyone have any clue if this is true?

creating test cases for -% physical and -% fire penetration, using flame sunder + fire sunder, tornado + fissure on a druid, and seeking out some physical immunes and fire immunes
in both cases: player equipped with no -% resist gear, level 55 elemental skills + unfinished synergies (Im too lazy to make 2 chars), mercenary is equipped with a 2x socketed armors, one with protectors stone modified to -200% resist, one with defenders fire modified to -200% resist
if working properly, immunes should take 5% damage
if bugged to apply merc -% resists, immunes should take 200% damage
should be very noticeable

test cases:
tornado vs phys immune (hell swarm, p8, kurast bazaar)
without merc armor equipped: they are taking tiny chip damage per hit
with merc armor equipped: they are taking tiny chip damage per hit

fissure vs fire immune (fallen, p8, blood moor)
without merc armor equipped: they are taking tiny chip damage per hit
with merc armor equipped: they are taking tiny chip damage per hit

No difference in damage seen in either case with my simple test

Great write up man. Ty for this response

i err, forgot the baseline case to just confirm the test is accurate and to chip in:

equipping that armor on myself:

tornado without armor vs immune: they are taking tiny chip damage per hit
tornado with armor vs immune: they died in 1 hit each, never saw hp bar drop, just dead outright

fissure without armor vs immune: they are taking tiny chip damage per hit
fissure with armor vs immune: they died in 1-2 hits (~90-100% hp), most dead outright

So to confirm: there's no evidence any -% enemy resist for elemental or physical was changed to work for player when on gear, it clearly worked when on self-gear but had no impact on self when put on merc
should still logically work for merc. And I do not know whether self+merc gear stacks to both work for the merc, with how they made the sunder stuff work or not. I believe your own sunder and -resists / -% dr would have no effect on merc, just on your own summons. But it doesn't matter either in this case, so I didn't test it. Just making the point that yeah phys damage chars do NOT need to put a protector's stone on their merc