Getting a kill when you are at critical is not easy to do on a consistent basis. Certainly not enough critical kills to gain a meaningful health return from this Dreaded Visage trait. This should be changed to when critical restore to full health on a kill.
First exotic titan build I did was with mask of the quiet one. Too bad I think the other armor pieces I had with it were sunset. Never really play anymore, but the next I did was with Ursa, and ran that for like six months. Man GMs were easy with that build. I think I had my super every one-two minutes. Every meaningful engagement I was the first to shield and provide that buff.