servent of decay unique not working on mercenaries

When equipping the Servant of Decay unique chest on my mercenary (Ranger), the expected Void Spawns are not being summoned every 4 seconds, as stated in the item's description.

Reproduction Steps:

Equip Servant of Decay on a mercenary (specifically a Ranger).

Enter any combat zone or idle area.

Observe for the Void Spawn summon effect.

No Void Spawns are summoned, even after extended time.

Expected Result:
Void Spawns should be summoned automatically every 4 seconds as described, regardless of whether the item is equipped by the player or their mercenary.

Actual Result:
No Void Spawns are summoned when the item is equipped on a mercenary.

Notes:

Tested on multiple zones and instances.

Effect works when equipped by the player character, but not when used by the mercenary.

Bug may be limited to mercenary interactions.

Same here. Sanguimancer, wearing nothing but Servant of Decay, not spawning anything in combat zones. With full gear either.