First thing to ask, have you gone all in with Stamina? Meaning all attributes and glyphs? Is your gear focused on Stamina? Have you picked Stamina Morphs? Got your Stamina Regen buffed?

In other words, Hybrids are not as good anymore. But, a NB still needs Magic. So, maybe something like 50 Stamina 10 Magic for you. The nice thing is, the magic you do use does not scale (Cloak, Veiled Strike, Shades, Mark Target, Fear, Sap Essence (that one and Veiled Strike might on the damage side but your using them for something else)). And, you don't cast the spells as often as you do other skills, so the pool can be smaller

And, you might as well get used to chugging Health Potions, as Swallow Soul is not that effective on a Stamina Based NB.

Anything that increases weapon damage will also help a Stamina NB, so Hundings Rage 5 Piece, Ashen Grip 4 Piece would be a good set to look at.

I usually use bow for single target and dw for aoe groups. Focused aim with Lethal injection does tremendous damage, esp with the execute buff to Lethal injection. Keep your distance to the target and you will deal a whole lot more damage. Without rally to boost your weapon damage, you have to rely on other buffs to keep your damage up.

Reaper's Mark is amazing, provided you use it on the smallies to get the major berserk. This, coupled with Merciless Resolve minor berserk can keep your dps up and have bonus Assassin's Will damage too.

Drain Power, works really well with Ambush and Steel Tornado / Whirling Blades. Use your DW to aoe down the adds, it helps that Blade Cloak and Whirlwind ( with whatever morph you choose to go with ) gives you that added benefit of increased weapon damage.

Use Evil Hunter as well if you go the Steel Tornado route, it's not as good as a stamina regain as Whirling Blades but the buff you gain really helps alot with your dps.

hope this helps!