As a bonafied survivalist I can tell you that while relatively high K/D's may seem to be more prevalent in terms of plurality in AH, they were far, far easier to attain in AW. My best camp in AW was 584 kills to 3 deaths; 2 augers and 1 to a "party wagon" buff gun crew, and I had many camps along those lines. My best in AH, just off the top of my head, was less than 30 to 1 K/D, my average tour much lower than that. It really has nothing to do with the relative quality of the pilots per se. It's the HO's and collisions more than anything else that are responsible for it. Simply put, there's more mitigating factors somewhat beyond your control that can ruin your flight in AH.
The perception that K/D is focused upon more in AH is an illusion created by the arbitrary separation of "Fighter" and "Attack" sorties. It's only evident when looking at someones scoresheet and noticing the statistical disparity between the two categories then taking the amalgam. If you combined all attack and fighter sorties for a given pilot I think you would find the average K/D worse in AH than in AW. In AW K/D was really the only metric able to be calculated by the available in-game statistics, in AH it is but one of several and the least competitive in terms of the ranking mechanism.