So, my main response to all of those questions is this: if the author handles the death in a sensitive manner, there is no need for a warning. That is to say, fictional death should be viewed as a plot device (having characters die without warning for no purpose is ludicrous), but should also be handled with care, keeping the emotions of both the reader and the other characters in mind.

I'm not sure if I'm really expressing myself clearly, but I guess my point is that I've read some really well written death!fic that left me bawling, but that I would have objected to have a warning for. On the other hand, I've read un-warned fics where a character dies BAM! out of nowhere, in which case I would have stopped reading in the first paragraph or two if I'd been warned about the death.