You know, there are many blamed for the "darkening" of DC, IDENTITY CRISIS of course being where it hit the not just breaking, but vomiting, point, Alan Moore and Frank Miller usually being blamed(though post-Crisis, I'd really blame Dan Jurgens, Mike Grell, and a few others). But the truth was that it was just the "Marvelizing" of DC. And that began with Marv Wolfman, who also wrote COIE. A lot of people forget that, as bright and round as everything looked, NTT was actually a pretty dark, dark book much of the time.
Coming from me that's not a criticism. I LIKED NTT, a lot, as a teen. But it is the truth: it started with Wolfman, and interesting that these things often come through Slade. This, IDENTITY CRISIS, and let's not forget the very first issue of INIFINITE CRISISS and the graphic impalement, between the tits, of Phantom Lady.