Personally, I find both the WH codex and DH codex boring and horrendous reads. I find any Pious literature very dogmatic.
As for the races themselves, they should be compiled into 1 Codex and made as either a force unto itself (you chose whether to Witch hunt or Daemon hunt, or a mixture)
scrap the Codex all together and put them in a FAQ for Codex MAARRRREEENS (of all kinds) and Codex limp guard.
This would be a way to keep enthusiasts happy, but scrap all that crap that festers on GW selves both in store and warehoused.
Neither race sells well. Neither race will sell well.
I'm sorry, but that's the hard fact. Converters/fluff players dreamboat maybe, but realistically, neither army has much of a fanbase.
Proof being the 200 pages of this thread of very little substance.
There's my point of view, now flame me you intolerant children!