Oskarm Nubuck Gloves does not trigger when mercenary hits an enemy

My mercenary does not trigger assassin's mark at all when he hits a rare or unique enemy.

I'm building my mercenary kind of like a curse bot.

I have vulnerability on hit, enfeeble on hit corrupted on the gloves (but they dont work without the corruption either) and assassins mark triggering from the gloves.

The mercenary has 276 mana available.
The mercenary currently has:
1 default curse limit
+1 windscream
+1 cospris will
+1 doedres damning

This should allow 4 curses, 3 from him and 1 one from me. So far I was able to apply enfeeble and vulnerability with him and assassins mark from me. Now I wanted him to apply enfeeble, vulnerability and assassins mark while I apply poachers mark.

The mark will not trigger regardless if I mark the target first or not (I just wait for him to hit first).

Please note the text on the gloves:
Trigger lvl 10 Assassins Mark when you Hit a rare or Unique enemy and have no mark

The mercenary does not have a mark (well, the enemy doesnt even have a mark, but an enemy can have 2 marks from different "players" if curse limit allows, just not from the same player) and it triggers on hit, not using gems socketed, which mercenaries cannot use.

To implement your idea, you will need a mercenary who has the required mark in his skills.