In terms of just length, I think this is perfectly fine for a piece of this structure and type. However the structure itself I think could use just a little bit of cleaning up. From my reading, it seems like you're going for a middle-out symmetrical structure. In terms of what your stanzas look like, and number of lines, it goes 5-5-7-4-7-4-5. So, your second-to-last-stanza is a little bit out of place. Assuming I'm right about what you're going for, which I might not be, I feel you can solve this in one of two ways. You could add a line to your center stanza, making it five to match with your other "Hush be upon us" stanzas, removing the symmetry altogether. Or you could add a line to that second-to last stanza. I don't think you should remove anything from your second stanza, because honestly it's really nice how it is. I love it, and it feels awesome to read aloud. But those are ideas for if you want to go the structure route.
Regarding flow, only one stanza gives me a little trouble, and it's the second one with seven lines. "The lantern of industry…" The first part makes sense, but the second half doesn't quite feel like it fits the rest of the piece, if that makes sense. It seems like you're trying to convey the sharpness and suddenness of an animal being hunted, which does come through. However… I don't know. I feel like this stanza could be reworked to still bring out the cruelty of its aspect, but feel less disconnected from the others in the piece.
I'll use the "coherence" slot to talk about something a little bit, er, 'high concept,' which you're entirely free to disregard if it makes no sense:
In this piece, you've built an interplay between words that are more 'round' and 'organic,' versus words that are more 'sharp,' and 'artificial.' To give an example, let's take this stanza:
Pungent breeze stirs silver trees; a white disc beats down unfeeling.
Far away and two nights ago, a cloud of billowing grey
Now bitter ash chokes sulphur air
and tarnished needles grey and blue
blacken dirt from red to grey.
Settled haze whirls in listless dunes,
a glass of time in lidded sky.
"Pungent breeze" is a very organic concept, if that makes sense, compared to the "white disk" which is both a clean color and a basic geometric shape. "Chokes sulpher air" compared to "tarnished needles" is the same sort of idea. "Listless dunes" and then "glass of time" is softer, flowy words, then glass is sharp and time is mechanical. I think it's super cool, but if you plan to rework that 7-line stanza I was talking about earlier, I think you can lean into that concept even more and drive it home, because it shows up a lot more at the beginning of the piece than at the end.
I hope I didn't bombard you with too much, and to clarify: overall I really freaking like this. The concepts come through, the tone is at a nice level of bleak. There's just a couple optional things you could do to take it to the next level. Fantastic work and happy writing,
-Piano
