User blog comment:Valyriefaery/Kaneki Will Take Arima's and Yoshimura's Role As The Emperor to The New Fool/@comment-27660519-20160815085409/@comment-25787298-20160816230946

It feels like AoT isn't very well looked into. Firstly folks, The manga is slated to end sometime in 2018-2019. Secondly, the 20th volume (which concluded in the chapter that Armin "died" in) was actually a decently paralleled volume to Volume 1. Go check out the parallels on the SnK wiki. Secondly, Isayama is a "write the whole plot out" type. Aside from some smaller details, he has the majority of the plot written until one of his assitants leaked it, leading to the story having to change from ch 15 (?) onwards. Now, he again has major aspects of the series planned, but kinks out the details. These last few chaps (Armin surviving the fall of all things; my excuse is the thickness of the steam actually slowed the momentum of the fall [poor excuse])  have been disappointing with the suspension of disbelief and more time was spent on this decision than it should've been.

My point is, Isayama isn't really winging it as much as some may think.