ive played with some DHs using turrets that seem to do just fine
The thing with the DH is you can get decent DPS output, but you have to be stationary and get set up.
When I run into a mob, I have to
1. Fire a single bola shot
2. Cast marked for death
3. Cast shadow power
4. Drop a <caltrops, turret>
5. Start firing rapid fire and wait for the arc of projectiles to rain down on the enemies
The first bola is required because it takes so long for rapid fire to actually hit. Shadow power helps keep me alive, but even with the dmg reduction active, I don't last too long until it starts feeding me lifesteal. When I do the initial bola shot, it lets me get shadow power up, take a few hits, and then gives me some life from the bola which tides me over until rapid fire starts dealing damage.
It's usually about 3 seconds from when I start this to when rapid fire starts hitting.
Going with spike traps isn't much better because of the 1.8 second delay.
I'm not good against single targets because most of my skills are AOE. I'm not super good against huge trash mobs because marked for death is a bit of a debuff in that the guy who spreads the AOE around also takes more damage and dies first, and it takes a while for me to start doing damage.
I am good against MP10 trash mobs and MP5 elites. I'm okay to not great against everything else, and that's with 300k dps.