[is it because he has no vision that he can use ice properly now? that the vision was holding him back? nehan has to push him even further.]

Fire, Diluc. [another sharp bark, nehan's tail wagging in irritation and impatience. then he takes a deep breath, and tries to figure out how to be a teacher, rather than an intense trainer.]

Focus, and use your fire. How did you feel, while using it with your vision? Use that-- don't think about the lack of it, but the freedom of movement you now have.