Blizzard confirmed the Nerub-ar Palace raid nerf is working as intended despite the visual bug.
For the first time this week, the Nerub-ar Palace soft nerf is available on live servers. The 
Severed Strands, however, is showing 0%. Blizzard confirmed this to be a visual bug and the buff is working as intended.
Hello! The Severed Strands buff tooltip showing 0% is a visual bug only and will be fixed in the 20th Anniversary Celebration update. The damage and healing bonus from the buff is working as intended.