I dare disagree. Compared to the past pieces of art, this image feels more dynamic. The old pic (the one in colour) felt more like silence before the storm, a heartbeat before they strike, and sure, it works, but here they're already clashing and for me, the image conveys this energy of it. Yes, part of it is obscured by the electric flash, but all it covers is part of Horus' armor, which, was it to remain visible, would make Emperor's sword lost in the background noise. Here, the flash contrasts it, outlining it very nicely, and the important parts about Horus - face and weapon arm - are visible. Ditto for Emps and Horus' expression, which I find to be a step above from the ones in previous arts.
I agree, the Emperor's pose is awkward. He looks like he's about to start running away from Horus and trips over his own legs. It's literally the only part of this image I don't like.
You (first link) are probably right about the space battle being created to be covered by text, but I like it. It also adds to the feeling of action and grand battle going on in the background. More generally, the fact that the background is blurred out only serves to bring out the main point of the image, which is Emperor's clash with Horus, and without blur the entire thing would seem like a static diorama - which, again, works for the old pic, but would work against this one.
The Custodes in the background do seem to be running out of nowhere, now that you point it out, but were they not there, it would leave an empty space which IMO would look kinda awkward, composition-wise.
The piece does make me able to imagine the scene of which it's capturing a single moment, complete with sounds, which I suppose is one of the points in its favour. And while I get why people dislike it's somewhat "digital" appearance, I like this sort of aesthetic, but YMMV on that.
All in all, I get where you're coming from, but it's still one of my favourite pieces.