Niles would much rather get SS3/mirror/sturdy impact in the A slot to improve his damage right away. Brazens are tricky for units who don’t really hurt themselves or don’t survive hits super well, and while Niles Res is ok for today’s standards his somewhat low HP means he can get oneshit by heavy hitting mages.
Speed Smoke isn’t really necessary as you’re not using the flashing blade check from his refine since you took the +2 spd refine instead. If you have the fodder for it, a joint drive atk, spd or res would be nice for him since they all improve his offensive capabilities.
I have a +10 Niles who’s somewhat heavily invested myself, and honestly focusing on his doubling for iceberg procs is what makes him scary. I don’t know how useful Deadeye will be on him due to his low attack, bypassing dmg reduction isn’t that useful if he was already only going to do like 14 in the first place.