This from the beginning of ch 13 WLW:
"Gods are epochal beings, not quite alive. Since the Now eludes them, they are forever divided. Sometimes nothing blinds souls more profoundly than the apprehension of the Whole. Men need recall this when they pray.
--Ajencis, The Third Analytic of Men"
I feel dumb for not noticing this before, but rereading it makes me think Bakker is holding up a great big sign saying "maybe the white-luck warrior don't know shit."
Also, that bit about the 'now' evading the gods...it makes it sound like the gods are split into two: past and future. This would fit pretty well with Birth being the past of all reality and War (as in death) being the future of every soul.
Onkis is really just a minor deity hanging out in Yatwer's domain. Yatwer looks at time and sees it progressing from the past to the future. Gilgaol looks back on time, sees what leads up to the inevitable death of persons and nations.