The Warlock’s Affliction specialization

Hello.

I’ve run into a bug that I’ve been struggling with for several days, and it’s preventing me from properly completing Mythic dungeons.
The Warlock’s Affliction specialization has a talent called Shared Agony, which is supposed to spread Agony to 2 targets within 15 meters, but this talent does NOT WORK no matter how close or far the enemies are standing. Before the expansion update on Wednesday, everything worked perfectly. What happened, and how can this be fixed?