Death Metal might have succeeded in creating and improving a form but they certainly haven't in applying that form coherently to express something meaningful.
I think you entirely misunderstand this genre.
Its poetry is the song structure composed of its riffs interacting to project a narrative form with a clear mechanism, like poetry.
- "Land of Ice" by Unleashed. Notice how the song builds to an internal climax and then smooths out into an entirely different timbre and riff style. Why?
- "Fall from Grace" by Morbid Angle. Verse/chorus, and then explanatory passages.
- "Hardening of the Arteries" by Slayer. Notice how each riff change has an introduction and these thrust the song forward to its conclusion.
- "Obscura" by Gorguts. Rotational form of riffs, produces sestina-like poetry.
Now compare this to classical music, specifically the storm Romantics (Brahms, Beethoven) and leitmotif-driven moderns (Wagner, Bruckner, Respighi).
I don't think structure is the same as content. Sure, you can use structure as a device to say something, but it's not everything. That's like focusing on the fact that a poem is structured AABBA instead of what the words in it actually mean. In an essay, it's not the structure of the essay that gets the message across, it's the statements made in it. The analogue of a statement in a metal song is the riff, melody, musical phrase, whatever.
You can rearrange a turd however you want, the result is still a turd. You can even rearrange it in very creative and elaborate ways, maybe even create a fecal reproduction of Bartonlini's Nymph With Scorpion, the result is still a pile of shit. This is how I see Death Metal. "Oh cool, they didn't make this song verse/chorus or this riff kinda develops off that one." So what? What you're describing sounds like another exercise in form to me.
I think the term "narrative composition" as applied to death metal on this site's articles is a huge misnomer. A "narrative" would imply that the songs actually have something to say and illustrate with the music, not just that songs are a bunch of chained up abstract noise that may (or may not) make sense musically and sound pretty cool but have no purpose beyond that.