Yes, you could use a Death Blessing. When Harry thought he was about to die, I think in Dead Beat when Morgan was gonna execute him, he made plans to use it for something to help Morgan and Luccio stop the necromancers, rather than use it against Morgan.
The main thing is that when you're a wizard who is about to die, you're most likely going to be focused on revenge against the person who did it. So that's the most common use.