Vincent truly was mortal in that moment Victoria took his strength. His ability. He would be easily killed like any human as Victoria used their bond and made herself more. So this was the hidden power of a peace keeper. It was lucky that they were the softer one, the part of their kind that did not seek confrontation or anger. That they couldn't feel it, because Jesus, how did you stop someone that could pull other's power into them. Including their learned abilities?