This is my current Nightblade build that I use in PVE.

I personally find this build to be pretty forgiving while still dealing out respectable DPS.

##### Tips for soloing: #####
Try to keep Rally up but make sure to not re-cast it until it finishes so you get the final heal when the ability expires.
Ambush to close any distance, stun your target, damage your target, and setup a buff for your next attack.
Brawler to perform and AOE, adds a bleeding over time effect, and will provide a damage shield. The damage shield will be higher depending on the number of enemies you hit.
Heavy or Light attack with your 2H as filler damage.

Try to keep your damage shield up from Brawler while also looking for any opportunities to Ambush your enemy. If an enemy runs away wait for him to reach his destination then ambush him to prevent his ranged ability.

Once your enemy is down to 25% health then use your Killer's Blade ability to execute. This ability does massive damage and also provides a heal.

If at any time your health gets below 80% cast Resolving Vigor to heal up.

If you have an OH Shit moment feel free to cast your Soul Tether Ultimate! This ability delivers an AOE stun while stealing their health giving you a massive heal at the same time. What more could you ask for in an OH Shit moment? Honestly I haven't had to use this ultimate during PVE as the heals from Killer's Blade, Resolving Vigor, and Rally seem to do the job quite well. With that said feel free to use your Ultimate as soon as it's ready for faster grinding or even consider swapping it out if you find another Ultimate more appealing.

##### Tips for dungeoneering or grouping: #####
Let the tank get aggro first. This is important if you want to live since the steps that follow are certain to attain aggro status otherwise.
Razor Caltrops your target(s) for AOE damage over time while slowing their movement speed.
Endless Hail your target(s) for more AOE damage over time.
Acid Spray for even more AOE damage over time while further reducing enemy movement speed.
Poison Injection each target for further damage over time. This does sick damage to targets under 50% health.

Try to keep up Endless Hail, Acid Spray, and Poison Injection in that order.

Again feel free to Resolving Vigor if your health dips below 80% to heal up.

Once you get the hang of the build you can start weaving your bars and abilities to maximize survivability along with sustaining decent DPS.

I don't expect the PRO's to use this build. However, I find this build pretty fun and easy to walk through any normal PVE content.

If you found this build fun and/or useful please give a thumbs up to give it more visibility.

Enjoy!