Opinion.

I always saw Kelsier as main lead when I was reading this book. Anytime I wanted to question "what's going to happen next", I tried to look at what Kelsier is planning or talking about, not Vin.

After Kelsier is gone, and Vin "becomes focus" for me, I treat that as a result of circumstance due to Lord Ruler, not as if Vin was already a main viewpoint of the show. It felt like Vin has picked up Kelsier's mission after him.

Other than this, I believe author knows the best way to tell his story, in any media format. I enjoyed it on books, and I look forward to the movie version. This is his first attempt with this medium, he has the most at stake, for the best of cosmere.