Condition Reaper is a powerful DPS team fighter that relies on Chilled for both control and damage. This build combines Harbinger’s high damage with Core Necro’s survivability and control. While Condition Reaper is susceptible to CC, it shines when paired with a support such as Tempest or Guardian.
Use the range of Staff and Scepter to deal ranged damage and soft AOE Crowd Control to maintain better positioning in a team fight.
Enter Reaper's Shroud to deal heavy melee damage. This can expose you to melee threats, so only use a few key skills, then reposition again to deal ranged damage with your weapons.
Chilled is the main source of control, but you have access to hard cc under the form of fear from Reaper's Mark and "Chilled to the Bone!". You can stow your weapon to bait "Chilled to the Bone!" animation. While using it in melee might sound good to you as it stuns for longer and gives Quickness, you should not focus on hitting this melee range, see it as an extra bonus you might get in some rare cases.
In shroud Executioner's Scythe is a hard cc and spawns a frost field under the target whether you hit or not, so it will always deal good damage.
A lot of surviving on Necromancer involves kiting and staying alive by taking less damage. Use your range to get free damage on enemies. Spectral Walk will help you a lot against melee specs who will want to focus you.
Use "Your Soul Is Mine!" often, as it has a very low cooldown and, despite its high healing, will rarely heal you back to full health due to Necromancer’s high health pool. It is also good to use out of combat (especially in spawn at the start of the match) to stack life force.
Being in Shroud reduces power damage taken by 50% and Infusing Terror adds a 20% reduction for both power and condi damage. Note that reusing it to fear with Terrify cancels the damage reduction.
You can replace "Suffer!" with Spectral Ring, to make it easier to lock onto a target at the cost of reliable cleanse and damage.