I can say they have fixed this problem. My friend in my guild needed help here and i already completed the quest/area, but whether its a bug or not, i was able to help him through every stage of the quest and i could see him and he could see me and i could kill his enemies, ect. I give ZOS a thumbs up to this fix if its a fix and not a bug.
Server: NA/PC
Holyringoblood (Altmer) Templer
Torgrimmer (Breton) Templer
Ringoblood (Nord) Dragonknight
Ringobloodtheold (Dummer) Nightblade