Has anyone read this story? In any case the entire run of TSR Fiction tends to go in the more traditional fashion so I'm thinking there has been some shift since OD&D.
I have. And to be fair the hero isn't heroic in the sense of Aragorn or Frodo, and certainly doesn't choose his journey. From the readers perspective, he's mostly mere protagonist, but he is described as being a heroic individual (where heroic is defined as doer of mighty deeds). That said, these sort of anti-endings were not uncommon for the literature of the time. Consider Heinlen's Stranger in a Strange Land, where while sf, the protagonist none the less dies at the hands of an angry mob.

Still, you can read the story for yourself online http://www.eldritchdark.com/writings...e-seven-geases