Fair enough, not your cake. Dan is definitely more concerned with the human aspects of humanity than with showcasing the 40k universe, at least until shit gets crazy much later on. And even still - the human side takes front stage.
It's all well and good saying he's writing about the human aspects, but when those human aspects aren't properly written to fit into the setting it makes them come across as badly written and dissonant with other books set in the same universe.
Let me put it this way, in most 40k books there's at least one human cast member, and I sympathised with most of them.
Wrath of Iron: I pitied the humans, respected their bravery and understood their horror at what was going on. They acted more or less how I'd expect people to act under the circumstances.
Word Bearer's Omnibus: Some of the best humans I've ever read, focusing on their responses to the horrors of chaos and the inhumanity of their own allies, and their faith and hope in the face of adversity.
Night Lords Omnibus: The humans in this serve as a fantastic contrast to the inhumanity of chaos marines and show that even heretics are human. (Personal favorite 40k story)
Death of Antagonis: A reasonably written, though poorly paced at times, exploration of why humanity is something that must be cherished but which you must be ready to sacrifice if the need arises. Largely focused on the sacrifice of of ones own humanity and why the horrible lifestyle in 40k is needed.
Storm of Iron: More humans who I respected and felt where good representations of the guard and the emotions they felt when dealing with the inhuman.
Compared to GGs where I spent most of the time going, 'Man the people of Tanith are whiny and ill-disciplined, and wow are chaos incompetent in this sector. Roll on Tyranids I guess.' It was like the Batman 'my parents are dead' meme but more annoying since they didn't even blame the right person or demonstrate any animosity towards the people who actually killed the planet, they just bitched that Gaunt didn't let them die there.
The only worse depiction of humans in 40k I can think of is from Siege of Castellax, where they piss and moan and freak out at the fact that *gasp* protein paste is people! AAAHH! *sigh* I was so happy when those humans died... At least everything else in the book was good.