The use of 'holy' here makes me think that
Not satisfied to simply drive the impure from their beloved Imperium, the Sons strive to purge it with holy fire. They have pledged to burn all that stand against Holy Terra. Where the cleansing flame strikes next, only time can tell.
By the standards of the Imperium and considering that the Age of Apostasy is just around the corner, I feel that labelling it tumultuous is odd.
The 35th Millennium was a tumultuous time for the Imperium of Man. In response to the ever growing threat of Chaos and the great losses suffered by Imperial forces, the High Lords of Terra ordered several foundings to bolster the numbers of the Adeptus Astartes. Under these orders, the Adeptus Mechanicus set about to organize and institute these foundings.
The last sentence above is also an example of some of the fat that can be cut from the article. We know that the Mechanicus organises foundings and we should be able to read into it without the sentence. Throughout the article there's a few more like this that can be cut to keep down the word count.
A touch of MISS in my opinion here. Plus it doesn't quite fit into the 'feel' of 40k, Inquisitors get the job done by any means: no pity, no remorse etc.
”They (the Sons) are true Angels of Death as the Emperor first envisioned them. I actually pity the impure that face them in combat.”
- Inquisitor Armon Vlox, reporting to the Ordo Xenos
Surely they would put in some provision to stop the violence in the Great Crusade. It doesn't look good to have your latest planet unable to be used as a base or part of the supply line due to the natives fighting one another. This needs to be better explained or removed.
The Great Crusade reached Pyron during one such period of peace. Pyron was added to the Imperium of Man and the leader of the dominant kingdom was named as Imperial Governor. As the Crusade pressed on, they could not know the course of havoc they'd set for Pyron. The wars began anew. Only now the fighting was over a new prize, the right to rule in the name of the Imperium.
Other notes on the Homeworld section- I think this section is badly placed. The opening little bit of the IA tells us about the chapter and then we're thrown into this section that doesn't contain a single mention of the chapter. It doesn't help with drawing the reader into the article. I would suggest moving it and/or adding more relevance to the chapter.
The Eugenics program- an interesting idea that hasn't been explored properly in a chapter (that I know of). However, I think it takes up too much space at the moment.
Currently, I don't think there's a clear picture of the chapter before the loss of their homeworld. It's hard to get a picture of how they change then. I think this probably would help us connect with the chapter better too.
I don't think you're exploring the full consequences of the eugenics program as well. A chapter is traditionally a brotherhood. In this, you have women training alongside your recruits (you even have them killing the boys in training) and then women becoming chapter serfs. What changes does this bring to the chapter's mentality?
Currently the article feels rather disjointed, I suspect because of editing and multiple versions not quite meshing with one another. There is not a good flow to it and the theme of the chapter doesn't really shine through. I'd have a look at making sure that it just flows nicer from section to section so they feel less like separate info-bytes.
Also, the theme of purity is one that has been done before, albeit not in conjunction with fire. I think that you really need to differentiate it more, perhaps by playing up the connection with fire. This could also be done by also highlighting their impossible task of eradicating Orks entirely. It's a task that they can't hope to complete but their hatred will make them try. It also explains the greater use of flame weapons, so that the Orkoid spores are eliminated. Either that or tie in more of the 'holy' hints that are mentioned occasionally.
Interesting ideas but I think the execution is just holding it back at the moment. Good luck with it