Problem with Dominating Blow using behead and the node Boon of the First One from Wildspeaker

Dominating blow minion kills using Behead support does not transer the buff from killing rare monsters to you while using the the Wildspeaker node that makes all kills count as yours Boon of the First One.

I don't know if this is working as intended but I was really looking forward to making this build where killing one rare would grant you 2 rare modifiers and have it turn into a rare sentinel too.