It offers an intensely positive outlook on Warhammer 40,000 in general and life in the Imperium of Man specifically.
Paradoxically, it does so due to a mechanism, which should serve to drive home the very depressing and uncaring nature of the setting and regime.
Starting characters in Dark Heresy have a reputation for being low powered, to a level where they could even be considered “ordinary people” (indeed the recruitment of some poor schmuck or other by the almighty Inquisition being the basic hook of character creation in the first place).
So far, so dark, with unwitting Imperial citizens or lowly servants being forced under in a maelstrom of incomprehensible intrigue and unspeakable horror on a galactic scale.
The brightness then suddenly shines in on this misery full force, once we go one step further though.
Ascension allows the very “ordinary people” we first met to climb to the (pen)ultimate peaks of Imperial power.
It’s not the specially gifted, one-in-a-billion exceptions who make it that far, for those are not among the characters in the first place, no, it’s ordinary run-of-the-mill people.
And thus, Dark Heresy marks out the Imperium of Man no longer as “the cruellest and most bloody regime imaginable” where no matter what you will not be missed, but rather as a place where even the lowliest can climb the social ladder, right to the top, triumphant against and within the system.