Have you thought about 2h instead of dual wield? I have a wicked magicka build but for stamina I'd say give 2h a try before fully commiting to dual wield. Dual wield isn't bad, I just prefer 2h as I know many do (at least from a PvP perspective). Rally is good to have until you unlock vigor. Having both isn't bad either but its a gamble losing another good ability. I would also suggest ambush and surprise attack. Killers blade isn't useless by any means however, wrecking blow and surprise attack hit hard enough to the point you can just finish them with that. Alternatively, you can use soul harvest as a finisher. It charges fast and if it doesn't finish them it at least hinders their ability to heal.

As far as bow, lethal arrow, magnum shot, venom arrow/poison injection are good choices. I would also suggest having 1 or 2 magicka based utility skills as a magicka dump. Something like piercing mark is good. Helps you hit harder and is great to counter other NB's who cloak a lot. Unless they do what I do, but that's my secret strategy

i just leveled a nightblade from 1-vr5 soloing most world bosses through vet content etc using 5 medium/2 heavy two handed build with wrecking blow siphoning abilities refreshing path etc. I originally started out dual wield and can say two handed is much better for both survive-ability and dps. With rally and heal morph along with refreshing path and siphoning your HPS is through the roof and your overall dps is pretty huge since your doing dps while your healing unlike other classes.