It really depends on what you want to prioritize in your build. For example if you MUST have the companion because you just love it so much, you're sacrificing another skill that could make your build completely different such as caltrops that would make you benefit more of your Steady aim passive. You could either remove your vault or companion for caltrop, that way you keep the mark of death that support your group( If you planned on playing with others ) You could also replace Hungering arrow with entangling shot considering you already have impale that is great against solo targets.
Try figuring out what you want in your build:
1. Play solo or with others? Have a support role in that group or more dps/survivability?
2. Do i want to hit hard and control mobs? Or CC/Support ?
3. and the most important in my opinion is to try to synergize your active skills with your passives to get the max out of them. I plan on using this build which is mainly based on crit, as i plan having a lot of it, i didnt get sharpshooter as i felt i would have enough and i could benefit more from the night stalker passive. Good AOE, Good CC, good support with the sentry+guardian turret and mark of death), but i dont have vault, mainly because i plan on playing with others ( aka more help if needed ).
Note how i try to get lot of discipline regen with Night stalker + Suppression Fire on my multishot, that way i can spam the sentry(as there doesn't seem to be a cooldown) and support my group a LOT with either health regen or damage reduction.
Also with the caltrop im getting more +10%Crit, Hungering arrow does more dmg when it crits and impale as well. The more i crit, the more disc i get. Etc etc etc http://us.battle.net/d3/en/calculator/demon-hunter#aZYjkQ!XeU!cccccb
Hope it helps!