I actually like that Brandon is letting the villain win. I'm actually willing and excited to say that it may be possible that Retribution wins in the back half and becomes the villain of the space age. It'd be a wonderful splash of terrifying that I just can't get anywhere else.
I will say, I don't agree that this WoB says "Cultivation created Retribution". She tried to make fix the Odium problem, caused a TOdium problem, tried to fix TOdium, and made Retribution. Her failure does not mean her plan was to make Taravangian even more of a problem. She's doing her best, but it's not enough.
Yeah, we still don't know much about Koravellium Avast (It took me forever to actually remember the Vessel's name). But Taln tried to kill Kor thousands of years before WaT. There is no precedence of future sight working on that scale (Mistorn Era 1 was 1000 years but this is a lot longer with more direct Shardic influence), and we don't know why Taln acted the way he did.