Well, the first thing I'd like is to know a clear idea of where "dark" is in this one. No sociopathic killers? Okay, but what if he makes a point to cut off left feet while leaving the person alive? The whole "hero dynamic" with optimism everywhere is usually what makes things "not dark" to me. So would we be dealing with worlds that are almost completely overrun, or would we just be "mature" as opposed to childish?
I didn't have a chance to step into the last attempt, as I didn't know enough about what information was being used nor had the time to get involved as it was starting. I'm definitely interested, especially if it's starting from the beginning again. Well... "En Medias Res" would probably be more accurate, since starting at the "very" beginning would leave almost no secrets to look for and give us an opportunity to prevent the problem from escalating to "world eating".
My suggestion? Figure out a baseline for "too far" and "good" with character concepts, describe the initial scenario (and if we're all required to be in the same location, or if we can stumble into each other as the story builds up), and get an idea that can be "used immediately" if people respond favorably fast enough. At least getting part of that together now should help get the discussion going, if nothing else.