WH40k Dark Heresy books + team forming issue

As Humble Bundle just released a bunch of Warhammer 40000: Dark Heresy rule books, I was just wondering about the issue of putting different characters in this game to one party.

It has a great setting (Warhammer 40k is a brutal,dark sci-fi/fantasy setting based on major troop-battles with one of the funniest representation of orks in roleplaying history), but…

If you start with “a guardsman, a tech-priest, a psyker and an outlaw are going to…”, it sounds as absurdly, as if you say “four popes are walking in the dungeons” in our world - there simply shouldn’t be a situation like this in a setting (or at least, very rarely). WH40k lore mostly focuses on major battles of troops - not to single or small group of diverse characters, so it also doesn’t help to form a team from a bunch of characters with different backgrounds.

Have any of you, who played/run with this game, found a reasonable “lore-friendly” solution to this or have you just ignored this issue?

Never played the game, but…
Maybe something like a passanger ship crashes on a hostile planet and the survivors have to form an uneasy alliance to escape (basiclly the plot of “Pitch Black”).
Or they are pilgrims who want to go to same holy place and they form a gruop because the way is dangerous (I think religion is a big deal in 40k?). (basiclly the plot of Dan Simmons “Hyperion”)

edit: Or they are the only humans on an alien planet and their racism brings them together (I think that is also a thing in 40k?).

Just make an ork boyz inflitration troupe. Would be a treat for a short campaign. And I would totally join.

@Xerdor: the pilgrimage in similar vein to Hyperion would surely fit, thanks for the suggestion.

@Resil: Ya gut it, humie - I just found a fan-made rulebook for orkz and I’ll definitely run a one-shot (or 'n Dakka). WAAAGH!

Ive got one answer to that… WAAAAAAAAAAAGH!!!