Spirit Link {PVP TALENT}

can someone help me out understand what the PVP Talent is supposed to do?

I was messing around with it in 2v2 today and it doesnt seem to actually work. is the effect negated if i am in CC? for example; had it on me and my partner vs rogue/mage. im sapped my partner starts taking damage but my HP doesnt go down nor am i broken from sap. same for if i was in sheep. (mage didnt dispel it i checked)

i heard it was terrible but if it doesnt work while in CC that just seems bugged?

Its an experimental talent that was useable for like one patch in Legion then got hammered by nerfs to the point of uselessness.