I’ve found fear is occasionally ending early on enemies. This was tested in pvp against dummies. Maybe its a dummy bug.
Runes: Necromancer or Nightmare.
Replicate test in pvp using 64004 traits obviously using Terror and Master of terror.
Procing fear using Mark of Reaper, Nightmare when hit, Doom, Fear of Death, and Number 2 downed Fear skill (harder to check because it gets to 4 seconds long). Duration on standard 1 1/2 seconds, skills states its 2 1/4 second duration after increases (3 for 600m Doom).
These dummies don’t use cleansing skills so i’m unsure why this is occurring. Maybe the damage still occurs but the fear damage float animation fails to play.