I'm reminded when I was reading "Heat Trace" a story I absolutely adore. But when I came to the part in which Bodie is responsible for the death of Murphy, I was suddenly hyperventilating a bit und I didn't continue to read until I knew Bodie wasn't a serial killer (what was not totally unlikely at that point). There I really wished there had been some sort of warning about that. Not necessarily an exact information about the plot but some sort of warning like "disturbing content" or something like that. I would rate the Heat Trace plot as major character death, other people probably wouldn't.
I do love dark and dramatic contend in fiction extremely (here and with crime fiction, too) but there's probably a thin line, were it could be too strong for my sensitive little nature. :) If there's a warning of sorts, I don't stumble into something too strong unprepared. As is said before there are times and places for certain types of fiction.
Also I think that gene/slash, AU or pairing information, hints about death fics and also ratings are a good and necessary thing. It doesn't necessarily mean that I avoid a certain type of fiction, I'm more faithful to an author than to anything else; if I like her writing, I often read everything that's on the market. Even within these information there's enough room for the story to surprise and I adore authors who do a wide range of different moods as myrebelcat. You'll never know what you'll get next.