I'm not going to bore everybody with details, but the only logical, world-saving, way out of the situation in the Gift was to let Dawn die. The only thing the audience 'deserved' was a story that made sense in context. The truth is this: There was no evidence anywhere in the whole season that Buffy's statement, that Dawn was made from Buffy's own blood, was in anyway accurate. Without that being established beforehand, Buffy's 'sacrifice' is just pointless suicide and the Joss-world should have ended. Is that a story I would have wanted? No. But it's the only one that follows from the whole season of episodes, if Buffy dies in place of Dawn. I suspect the notion of Dawn having 'Summers blood' was supposed to have been introduced in the course of the arc, and someone was doing a horrible job of supervising story continuity that season. Joss didn't seem to care.