Let's keep it simple:
Abnormal foot pronation (during stance phase of gait) is any pronation that is occuring when the foot should be supinating.
According to the research of Inman and Close, the pelvis (transverse rotations) should drive the motion in the foot: Internal pelvic rotation will pronate the ipsilateral (same side) foot. External pelvic rotation will supinate the ipsilateral foot.
From heel contact to foot flat, the foot should be pronating.
Any pronation past foot flat, is by definition, abnormal pronation.
For more information on abnormal pronation, read the discussion of the Podiatry Forum at:
http://podiatryarena.com/index.php?threads/defining-abnormal-pronation.111866/page-2
Comments
Ultimately, regardless of condition or ailment, our feet remain our foundation (and foundations ought to be as strong as we can make them). As such, while you may focus upon improving hip flexor strength and flexibility, for example, since you've evidently dismissed their importance, while hip alignment remains important, don't neglect your feet.
Start practising balancing on one leg with eyes closed (if you can) to improve proprioception (awareness of movement), thus, encouraging intrinsic activation of the many small muscles that comprise your feet. Doing so should allow you to appreciate just how important our feet remain.
FYI...as I'm a bare footer and barefoot runner, possessing over a decade of experience/research into foot health, also helping people correct dysfunction within their feet (I read medical journals too), I don't wholly subscribe to the notion you've put forward.