What is the biggest change you've made based on alpha/beta reader feedback? (This goes for any of your books)
Probably adding Adolin as a main viewpoint character in the first book, which was done because I had trouble striking the balance between Dalinar worrying he was mad, and being a proactive, confident character. Worried better to externalize some of the, "Am I mad" into his son worrying "My dad has gone crazy" while letting Dalinar be more confident that his visions were something important. (I still let him worry a little, of course, but in the original draft, he felt temperamental from vacillation between these two extremes.)
Bringing Adolin to the forefront in the books has had a huge ripple effect through them, as I've been very fond of how his character has been playing out.
May I ask why you choose to use Adolin as the viewpoint character to supplement Dalinar as opposed to Renarin? My understanding is Renarin has always been the "most important brother" within SA, which made me wonder why, based on the beta readers comments, you ultimately decided to use Adolin and not your established character to bring forward the dilemma.
I am, obviously, extremely fond of how Adolin has been played out so far and while I have no idea where he is going (but zillions of theories), I am curious to know what his initial purpose in the story was. Did you draft the character's personality just for WoK's needs or did you have an idea of what to do with him when you made the change?
I was well aware that I needed certain things about Renarin to remain off-screen until later books, and him being a viewpoint character early would undermine these later books.
Adolin is a happy surprise and works exactly because he doesn't need to be at the forefront, even after I boosted his role. With Adolin, what you see is really what you get, which is refreshing in the books--but it also means I don't need huge numbers of pages to characterize him, delve into his backstory, etc. He works as a side character who gives more to the story than he demands pages to fullfill that giving, if that makes sense. Renarin is more like a pandora's box. Open him up, and we're committed to a LOT of pages. (Good pages, but that was the problem with TWOK Prime--everyone was demanding so many pages, from Renarn, to Jasnah, to Kaladin, to Taln, that none of their stories could progress.)
Adolin has basically always had the same personality, from TWOK Prime, through the original draft of the published TWOK, to the revision. The changes to making him more strong a viewpoint character were very natural, and he has remained basically the same person all along--just with an increased role in the story, and more development because of it.
I do discovery write character, usually, as a method of keeping the books from becoming slaves to their outlines. This means that Adolin has gone some new directions, but it's been a growth from the person he was in TWOK Prime. (Which you'll be able to see when I release it, sometime in the hopefully not distant future.)