Any ability that reduces a character to a single roll of the die is always a dick move. Yes, I did just call thousands of DMs and a myriad of game designers dicks. Its lame enough when players do it, but when the DM with essentially infinite resources does it, it becomes infinitely pathetic.
Friends don't let friends use save or dies.1
1Does not typically include save or lose, which generally will require two rolls or actions to kill anything.