Here's my little fun condi build for core necro harder PvE:
Great sustain, despite being condi (amazing heals, strong anti-condi, reasonable life force generation, some protection)
Fun, fun FUN!
Respectable condi damage (for a core build)
Easy to change to your tastes (no problems going terror build with this, getting more anti condi, or more cc)
Expensive (trailblazer + rune of tormenting costs)
Generally you do what any condi necro would do -stack condies! But here you reap massive payoffs in self healing when you do!
Blood Bond will heal you for huge amount of health every 20s or so, as long as you put a 4th stack (or more) of bleed on something.
But the real star of the show is Rune of Tormenting - each single stack of torment you apply will heal your for a small amount, except if you play it right (5 condies target + devouring darkness + other mobs nearby) that small amount will jump up to even 5k heal each 10s.
What's that? You want more?
No problem - how about 6k from tainted shackles? Go into shroud, tether yourself to victi....targets, then pop out and the remaining 3 pulses of shackes will heal you!
Plaguelands...well....if it has torment and bleeds (hint: it has, a lot!), you're getting your rear healed again.
And what is that blood is power doing there you ask? Well...whatever you want it to!
Cast it (it'll still heal you, cause rune of...you know the drill), then use staff to transfer condies to enemy - why waste a good condi?
Not too impressed? Then cast well of power before BiP and watch your torment get converted to might! Then anotehr BiP cast, more might...and might from well of power...and might from BiP itself...yeah it's a "powerful" combo.
Or you can just slot consume conditions and eat it! your call!
Or unholy martyr to fuel your lf bar....
You have options, you pick!
Other then that you get protection from your well of Blood and well of power (given you won't forget that you even have a healing skill with this build) and spectral grasp is there to round up your medici...enemies for those juicy 5 target torment casts. Feel free to change it to epidemic if you feel the latter is more needed, but be warned epi bounces will not trigger rune of Tormenting's healin.
Other then that same old - good cc (warhorn 4, shroud 3 fear and shroud 2 chill, staff chill and fear), long lasting condies and general aoe condi havoc and mayhem.