According to the changelog, and the in-game description, Death Pact should get refreshed whenever making a kill. Currently, it does not get refreshed.

Also, the changelog and tooltip say that making a kill while affected by the BUFF give permanent damage (and refresh the buff). But right now, the damage is gained when an enemy DEBUFFED by the armor reduction gets killed by anyone. If this behavior is intended, then the description and changelog should be changed.