This Build isnt tested for Trials yet.

This build aims for a viable vampire-feel NB. It pairs high survivability with potentially very high damage (due to simmering frenzy)

This build is as most builds, build around simmering frenzy, which allows us to sacrifice a lot of HP for extra damage (if needed). Due to the Mythic passive of the Pale order Ring, we heal for the damage we do, so we can use simmering frenzy rather safely.
Basiclly more damage, means more sustain which is a very satisfying playstyle.
You can customize your build in many aspects
E.g.: if you struggle with the "Simmering Frenzy" self inflicted damage, swap it for its other morph "Sated Fury".
You can also swap "Twisting Path" for "Refreshing Path".... and so on
Also "Crimson Twilight Set" can be Swapped for a pure Damage Set, like "Mothers Sorrow Set", if you want to go more offensive.
You can even swap weapon types, since you only benefit from the passives, and dont use any weapon skills. And tho Destruction Staves offer good dmg, you could go for a 2 Handed Playstyle for AoE.
Your CP points are personal Preference. You should focus on Selfheal, Crit-Chance, or flat damage. HP wont hurt aswell.

Due to "Blood for Blood", "Simmering Frenzy" and the "Pale Order" Ring, you wont be able to be healed by others 99% of the time.
For VET-Dungeons (youll be fine without a heal in normals) I suggest getting rid of the "Pale Order" Ring, due to its nerf within a group (20% Selfheal -4% heal for each group member) I suggest getting a full monster set instead. Also "Blood for Blood" Which is our main Spammable, makes you unhealable for 3 sec, and so does "Simmering Frenzy" while its activated. Swap those out for any Skills you like, but at least one spammable.

The Basic rotation is very simple.

Buff up with your backbar,
Mark a weak enemy with "Reapers Mark"
Switch to Frontbar and cast "Sap Essence" (can be spammed if you need heal and AOE)
When you have all Buffs activated, cast "Simmering Frenzy" and Spam away with"Blood for Blood"
Remember to Light Attack in between "BfB" Casts, to make use of "Siphoning Attacks" Passive, and to stack "Merciless Resolve"

Your Ultimates are also Situational, since both give you a relatively good damage boost for their Cost
"Soul Harvest" increases your Damage against the Marked enemy, and its Passive provides you with Ultimate Stacks
"Swarming Scion" Gives you flat stats and more survivalbility.
Remember more Survivability mean, longer "Simmering Frenzy"
More Damage, means more Survivability due to Lifesteal
Chose accordingly what Ultimate you need. Just dont safe up 500 Ult