Hey,
I've been playing [Ash] for more than a year now and he is technically my "mainframe".
This build focuses on making you invisible for most of the time and with [Rolling Guard], you can remove status effects that might prove deadly in certain situations, as well as giving you an opening to cast your invisibility again. The added strength is mostly for stripping 100% of the armor off of hard to kill enemies. Arcanes are optional and a preference, as well as based on my personal experience with the frame. Many people use [Guardian] but I think its meaningless. The rationale behind it is that if you want an enemy to hit you to proc an arcane, you'll die most likely when it comes to high level enemies.
The added range helps in activating ur 4 on farther targets, and I kid you not, [Ash] 4 with 12x combo multiplier is VERY deadly.

NB: if you do not like this build its fine, I didn't like any of the builds on the site as well. Use this as a template for what you want your [Ash] to be. The frame is very flexible when it comes to modding, so testing out different builds is important to see what you are most comfortable with. Remember [Ash] is not popular frame when it comes to gameplay since, without doubt, many frames fit better in most situations. Yet, I've played with this frame almost non-stop for the past year and it seemed to work for me.

Final note: you are a ninja, so I expect no less than most damage done and least damage taken. Learn to be agile and maneuver your frame throughout the field like a breeze and you will master this frame.

Subsuming tips: Test what you like :p. I tried defy but never even used it, warcry and it didnt really feel nice, and finally [Nezha]'s 1 ability and that seemed to be my favorite. The added speed and free status heat really helps in endgame (levels 500+) enemies.