Ok, I've actually red (read: skimmed) it all. As an avid writer myself (*subtlely points to signature*) I do have some pointers though.
First, while there are some great snippets of story there, I'm completely lost on the overarching story. There are so many characters that it is hard to care for any of them. Also, the is a lot of 'how' in the fights (shooting weopons), but hardly a why or where to acompany it. There was something about a waagh, but hardly any backstory on it. Also I have no idea how the world/battlefield looks. Is it a swap, deser, or city? Besides that, writing good action is HARD! (boy, do I know that). A little bit more of an elaborate writing style may help here. Instead of 'He fired his storm bolter and the heads of five orks exploded." you might want to go with a bit more of a "His stormbolter kicked violently in his grip as the high explosive shells of the massive weapon left the barrel screaming toward the Orks charging him. His aim was perfect, shifting from one target to the next, each round vaporising the malisously grinning skull of the greenskin unlucky enough to cross his crosshairs."
If the reader cares about your hero, they will be even more shocked when he finds himself in a seemingly unwinnable position, or when you 'kill' him only to bring him back later with a heroic story of survival. This will keep the reader on the edge of his seat and will make it so he wont be able to stop reading.
As a disclamer, no I am not a profesisonal author or anything, nor do I think I am comming even close to that level. I've just been writing for some years now and think I am reasonably good at it. (for some of my work on colaborative (rpg style) writing also check http://www.ussaeon.co.cc/ I'm on there as "Idar Prius", Arachas can be found there as Bel Moroi.