After killing Zulmak in the Pit of Heresy dungeon and waiting until the mission end timer runs out to see final damage, the Activity Summary shows 0 damage on Zulmak (despite him having 1,953,449 health in previous seasons). I noticed on a few recent solo runs that the damage was showing 0, and comparing it to a previous screen capture, the stats are arranged in different columns now with Zulmak Damage previously being first in the far left column, now last on the far right. Don't know if the change has anything to do with the bug, but TL;DR Zulmak Damage is showing 0 (at least for Solo runs, I haven't tested with a team).