Maybe this is blasphemey but I'm pretty sure it's just not consistent because Brandon made a mistake and it's too late to fix it. Proposing more and more complicated models to explain an inconsistent phenomenon is bad science.
I live Rlain being a bondsmith and I really like Shallan's arc. I agree that Venli's seems repetitive and not as original, but I think a lot of her arc will benefit from details about the singer occupation. My main protest is Adolin becoming a radiant. He's just not broken.