Yeah, I don't understand you. You have a favorite character and you want him dead only for the sake of questionable perspective that characters who now are "boring as sin" would suddenly stop being boring? What if not? Adolin is boring not because Dalinar overshadows him, but because he's poorly written side character with no purpose in the story. He isn't a planned character and he has no satisfying character arc because of it. And he never would. Sanderson stated it multiple times: Adolin is a side character, do not expect much. If you give Adolin more page time he won't become interesting. He'll remain wooden and boring character with more screen time. Renarin will have a big role in the second half, so don't worry about him. Main characters for the first half are Shallan, Kaladin and Dalinar.
If Dalinar had died on the Tower his amazing story arc from Oathbringer would never happen. And this is the best character arc in these books so far. All you mention here: Adolin/Renarin working together against Sadeas, investigation into Sadeas murder, sounds boring and nowhere near Dalinar's story arc we have right now in terms of excitement. Sorry. Existing narrative is...just better. Don't know what Sanderson plans for Dalinar in book 4 and 5, but I'm sure, it'll be great as always. His character development is much more interesting than majority of SA protagonists.
Dalinar overshadows other characters? Really? If someone overshadows other characters it's Kaladin. Kaladin who stole the second book from Shallan, who always saves everyone during his "moments of awesomeness". Fortunately, Sanderson understands it. If you want to kill someone who overshadows everyone, kill Kaladin then. Absolutely agree with @RayW2
