I think the main issue is a matter of tone. Although mytical, the first two games had a very no-nonsense charm to them. I'm with you here, I think they simply needed more time to polish those ideas with HW2. This in a conceptual level. I also think that the dynamic difficulty actually punishes the players who do well, but that might simply be me being whiny.
Your ideas are actually quite good here. An expansion or plain sequel with DoK could flesh out what needs to be known about the past and HW3 would plunge us into a more fleshed-out future. I would love to see that, indeed.