This moment feels not unlike when the bar finally learned what really happened when Boo disappeared. Only, Rabastan wasn't thinking 'what if?' thoughts—he was thinking 'I'm gonna do this' thoughts.

"You could, but it depends more on how he died. Some ways of dying you can't do anything about but make it easier on the person about to die."

Because you can die from mundane things, even in Milliways. And Rabastan has no idea how Doc had perished.