This build is lacking two key components of survivability- Healing and Crowd Control. Without these you will have a difficult time killing anything without the help of a group.

Suggestions for healing: Rally (also gives 20% damage buff) and Vigor.
Suggestions for Crowd Control: Mass Hysteria and Dark Cloak.

I think your build is a little scattered, your not really playing up to the Nightblades strengths. I believe you have to play up a strength whether thats ranged or melee and then your other bar should be buffs and tricks to enhance your survivability. have you considered vampire? I know werewolf hits like a truck but I also see them die really quickly, vampire gives you more survivability imo and adds to the whole hit and run playstyle a nightblade brings to the table. I know everybody has their own playstyle so if this works for you and your having a blast then just ignore me

I would ditch steel tornado - you already have Assassins Blade, you dont need two executioners. I would stick with Assassins Blade since it adds to your overall crit. I would replace ST with Mass Hysteria which is one of the best Magika dumps for a stamblade and is also one of the most powerful cc's in the game. Also, I like Flying Blade alot but I would replace it with Camo Hunter, this will dramatically improve your crit and also can be pretty devastating damage wise.

If your absolutely deadset on running a bow I would definitely drop arrow barrage, its not all that effective in PVP - replace that with Dark Cloak as a means to escape and purge dots. If it were me the only bow ability I would even consider would be Poison Injection, its a really great dot for utility. Dont get me wrong Focused Aim is really solid especially for a bow, but I would run Relentless Focus Instead, this gives you burst but more importantly gives you an overall 8% damage increase, more crit. and Stamina Regen. Shadow Image is a really great under utilized skill, I only think its useful if your running Dark Cloak though. It also wouldnt hurt to consider Vigor on your bar if you can find the room for it. I think thats the problem with NB's in general, so many great skills not enough slots...