Wow, I liked the dark Kaladin chapters in WoK, and the Shallan chapters were like the light in the dark for me. I love the interludes, and it always surprises me when I read that the interludes break someone's immersion. They were interesting bits of worldbuilding I looked forward to, and I needed the breaks. Rysn is a particular favourite, the only interlude character appearing in all 3 (soon 4) books, seeing Shinovar & the Reshi Isles was interesting! Her part in Oathbringer tied up directly with the main plot, and coming up next, she might visit a land of longstanding mystery on Roshar.
I have to admit I liked Dalinar's chapters less in WoK, but it had little to do with boredom. Same with WoR Shallan. I have no complaints with OB.
So, no one, there aren't any characters whom I found boring.