I just created a fun Ballistics build a couple of minutes ago and tested it to see what I could come up with:http://us.battle.net/d3/en/calculator/demon-hunter#bcjgRS!hX!YbcaYY
You use specific skills depending on the monster type and formation.
Nightbane is to be continuous throughout battle.
vs. large formation of monsters, you use Arsenal and inbetween Arsenal shots you fire off Justice against the monsters closest
to you, while stutterstepping. Between Nightbane and Justice, you can Arsenal repeatedly till everything is dead.
vs. scattered monsters around the area, pick them off with Fire Support
vs. the front line of monsters, use Fire Support and pepper the area
vs. larger high health targets, Mortal Enemy into Fire Support
vs. elites depends on affixes, Mortal Enemy closest monster to you and Fire Support. If the monsters are too fast, tag closest one with Mortal Enemy and sutterstep back and go into Rocket Storm. If you become completely surrounded Mortal Enemy any target and Rocket Storm out.
Remember always to Nightbane before Fire Support or Rocket Storm for the life steal, and continue to Nightbane throughout for the Hatred regen.
If you're bad at stutterstepping, use a slower weapon to channel longer and use Rocket Storm to reposition.
Ballistics sucks anyways, but this build was pretty fun. Whatever MP you have enough damage and defense for. If you outgear the MP, Arsenal is enough to wipe trash, and Rocket Storm is enough for scattered trash. If you're undergeared heavy reliance on Fire Support keep monsters in a straight line and fire RF offscreen as your first order of business.
With slower weapon you can go:http://us.battle.net/d3/en/calculator/demon-hunter#bcjghS!hX!YbccZY
And keep Shadow Glide up to move through the content fast.