noticed inner sight was not working at all during the world boss today. I thought it may have been bugged due to a group with someone using barber heart. But than I ran into butcher and it wasn’t working with him ither. only just noticed this today.
Hey had same issue just now and i was wondering - so took a dung without my m8 with barber and then it worked fine on bosses. so best fix for now is play without people who has it on 
Same here. This issue is documented here and in other places on the forums and reddit. Hopefully will be acknowledged and patched.
my rogue inner sight is bugged on bosses if i play with/near other players. i played nightmare dungeons with a sorcerer for a couple days & every time we got to the end boss inner sight would not fill and the mark was on the bosses i was fighting. Then today i went to Ashava world boss, no party, just being around other players, and again my inner sight would not fill up. Boss times are when i need this working the most so…blizz, consider the bad words as spoken 
I just fought the butcher with someone in my group running the barber, but who was on the other side of the dungeon at the time and totally uninvolved in the fight, but I was unable to proc inner sight. Seems the bug persists…
Still not working, Blizzard please fix this…