You are absolutely right. You have no escape ability. Unless you are absolutely confident in your ability to not get surrounded, you can kite your life away (no pun intended). I would personally drop shadow power for Vault with the no discipline cost rune.
Why is this?
Well, shadow power uses as much discipline as SS - which is far more important for breaking CC (frozen, etc) and dropping aggro when playing in a group. Sure, shadow power reduces damage taken, but only for 3 seconds. 20% lifesteal can be nice - but generally its not going to save your life. Nether Tentcles already gives you the little bit of lifesteal you need.
With vault you can vault while jailed, and vault THROUGH enemies. This is very important as it allows you to not get cornered or trapped in within walls.
This is how I would set it up. http://us.battle.net/d3/en/calculator/demon-hunter#bRdVXY!caT!acYbZa
With cull of the weak, you have great synergy with Your primary and Secondary attacks.
The crit per second gives you a huge DPS increase, but you can keep brooding if you want. ?Once again, Brooding is not going to save your life, killing things faster will - I guess brooding can save your life when your running from things though...Your call on the last passive.