As a dark ranger, you want to spec towards bow damage and your mana pool. Save skillpoints for Bone Shield, Bone Spear, Bone Spirit, Bone Wall, Confusion/Attract, and Corpse Explosion. Go jewel hunting for a set that would provide a huge boost to one of these aspects, you want to act like artillery, you're no tank, you're barely a caster compared to most other necromancers. What you wanna do is cause as much chaos as you can from a backline, with others like barbarians taking the damage for you.
If you can, record Dark Ranger sessions, put 'em on Youtube, I'd love to see how you handle it.