The rules failed at the fundamental level of actually evoking the setting an theme of the game.
I disagree on a fundamental level. Dark Heresy has always been essentially Cthulhu in space. It plays like that. It has involved combat, and an involved sanity system that makes the characters eventually unplayable which is a core theme of the Warhammer universe as a whole.
I really hate what they did to the Warhammer Fantasy system as a whole. The special dice and cards...cards, don't get me started on cards.