What is far more bizarre is that one of Padra's brothers has "dark hair from his wetlander side".

His only "wetlander side" is Rand via Tigraine, so to speak (Rand being half-Aiel by blood). Tigraine is a blonde (her brother is a redhead). More importantly Rand is a redhead, so he has to carry a pair of recessive genes.

I don't think it's even possible short of a genetic anomaly for a blonde like Aviendha and a redhead like Rand to produce a child with dark hair and colouring as Brown is dominant over both. If Tigraine was carrier of one brown gene, she'd have had brown hair. It sounds like Brandon wasn't careful with the genetics in that chapter, or worse he messed up and was thinking of Tam as the "wetlander side", forgetting as he wrote that Tam isn't Rand's father and Rand's father, not mother was Aiel (and that in the TR where blondes and red hair are totally unknown it's most unlikely Tam would carry a recessive gene for blonde hair anyway...)

Channeling disappearing might be odd too for the same reason, though it's at least easier to explain, since it only required Padra to have children with a man with an heterogenous sequence or a pair of dominant genes (not rare even among Aiel) for her ability not to appear in her offspring. Mind you, she was Maiden of the Spear and it seems Brandon decided that just like that or without any explanation for the change Maidens in the first decades after TG no longer refrain from recognizing their offspring or marrying (or having children in the middle of fighting as soldiers in a war, apparently). The Maidens have recognized Rand as Shaiel's child, not put an end to their old ways as we can see with Chiad and Gaul.