Death as anything other than an end to a character seems more an attempt to comfort the all too human anxieties surrounding our end. We each are promised death, but many flock to notion that a omnipotent deity or advanced scientist will somehow bring us, or a part of us back. Or that our legacies will survive via our children or works. Either way, we fear the end and hope desperately for something otherwise. I find stories that deny a true death tap into our hope in way that can be dreamlike. Doctor Who was an example used already. The character is in themselves a dreamy figure in that death is a temporary, superficially changing thing. They are deep, emotional, intellectual, and come with a range of challenges and successes that is all too human, however, the last bit that makes them awe-inspiring is their lack of coherence to our biggest rule -- all things die. I don't mean to say that Doctor Who does us a disservice in its fantasy, I love it, but we should definitely separate that bit out and remember to face ourselves. as we consume these stories.

I think it's important because people are historically very bad at discerning fantastical stories worth knowing and literal truths. We take cultural histories and stories known to be meant to teach symbolically and we swear by them as fact, we even kill for them. Too many of us are just sad, grasping at anything to convince us that life is more even when that form of salvation exists down other paths. So I say taking the death out is a great tool for some stories. I also warn that doing it taps into us like speaking about sex. There's something deep within us that keys up to the topic of death and is willing to believe just a bit more. After death is conquered in the story and your belief soars beyond one of the greatest limitations our world offers, I doubt too many other obstacles will provide the same level of tension. 

Gotta say though, I found the Night Angel series as a great story that conquers death yet continues to wind one up. Check it out!