I felt that he was the weakest characters in the series, actually. Everyone else seemed to be better developed than him, but that he was needed to link everyone together.
This series is (if you somehow missed it) very influenced by Baccano and Baccano had the same problem with having characters that barely had screentime or development but were still vital *Cough*DallasGenoard*Cough*
Well tbh there wouldn't be a Durarara without him there would be no dollars and every character would be scattered and the anime would of turned out bad
Baron: Yeah I think so too. But Dollars was founded by him right? And Dollars seems to be having the most members :) But in terms of fighting skills, he is the weakest of them all compare to Yellow scarf and Blue Square. Is Baccano an anime also?
Anyway, I still think that without his present, Durarara will never ever be Durarara.. xD Actually from the beginning I already have guess that Mikado is "someone". Then when they started to mention Dollars present in the city and they say that they never met the leader of Dollars, I have the slightest guess that Mikado was the leader. xD