It's just a thought. Don't take it so seriously ...
For some reason I believe the Dark Ranger would be a mix of Rogue Subtlety + afflic Lock + MM hunter.
And let me now dream that I'm one of the developers ...
I would make this spec with the following skills:
Stealth (replacing camouflage)
Fear-Arrow (an arrow that causes fear for 4 sec. 15 secs of cooldown)
Dead beast ritual (sacrifices your pet to guarantee 100% crit on its first stealth attack).
Dark fashion (allows the Dark Ranger to use any leather armor to increase its attack speed by 20%)
Yes, such a spec with the skills above would be enough for me to drop my main rogue and never come back ...!