Culling strike on item

Hello,
I have unique gloves with culling strike on them . While I have them on there is no visual indication on enemies that they would die with the next attack as with Killing Strike. Also, I am quite sure that the execution part is not working on the enemies while I have these gloves on as I have tried to test it and normal enemies stay alive with much less HP than 30%, but I could be wrong.

Best regards,
Madragor