Knockback, along with pierce, and exploding arrow are a life saver with this build. If you are planing on using a demon machine, consider Chain lighting as one of your other attacks.
Here is a great post on this topic you may want to check out:Click
Very fun build good luck with it :)
Numsay
Here is a great post on this topic you may want to check out:Click
Very fun build good luck with it :)
Numsay