Grimtools:
New Spec
Old 1.2.0.3 Spec
1.2.1.2 Changes:
A lot has changed since I made this build. This new Spec is definitely a lot better. Performance Updates in the comments . Mainly new Devotions and a new Relic.
Forword:
There are already multiple Cold damage based, dual-wield Reaper’s here, but I think most of them are outdated and / or have some flaws. I think my iteration strikes a good balance between tankieness and damage, leading to a character that can clear all content in the game.
Idea:
Well the idea is simple, get your auto attacks (AA’s) as strong as possible.
Build Concept:
Nightblade and Nercro already provide a lot of damage and leech, leading to a lot of the gear being more tanky oriented instead of going all out in damage. Beronath’s Fury is a must AA replacer and the Weapon Pool Skills (WPS’s) Execution and Necrotic Edge are the main stars of the show.
Ingame stats:
Gear Discussion:
Weapons: Malkadarr + Chillstrife, Malkadar provides the damage while Chillstrife gives up to 10 % Resistance Reduction (RR) if night’s chill is not hard caped. From my playtesting this is the best combination of weapons due to Necro not providing any cold RR and together with the Medal, Necrotic Edge is already a 360 ° AoE nuke.
Rings: Well these are best in slot (BiS) but if you don’t have these yet, you must run Ill Omen for damage reduction (DR). Because The DR only procs of off crits, this build needs high Offensive ability (OA), forcing the pumping of cunning. If your OA is above 3.2k without cunning pumping, feel free to pump spirit. 3.3k OA feels like the sweet spot.
Head: Namadea’s Horns, needs Overseer Prefix.
Legs: Reaper’s Legguards are definitely the best here. For my Callagadra kill, I used Deathwhisper for + 6 % Phys res. Feel free to use either of them.
Feet: Still close between Primordial and Waraithwalkers, pick your poison.
Relic: Nemesis or Serenity, with the new spec Nemesis should be fine.
The Rest is self-explanatory, trying to get as close to 100 % Vit → Cold.
Key Devotions
Murmur: RR
Viper: RR
Rhowan’s Crown: RR
Leviathan: Because the Leech of reaper is already high enough and there is no Acid / Lightning → Cold conversion, I feel Leviathan is the best here, providing 18 flat cold and nice tankiness.
Play style:
Try keeping Lethal Assault and Soul Harvest up 24/7 and use Ring of Steel for the Fumble. If you feel comfortable, use Mark of Torment to reflect Sunder, else use it for a tankieness boost.
1.2.0.3 Performance:
Ravager of Flesh in 1 min 1 sec.:
Callagadra in 1 min 47 sec.:
Crate in 1min 17 sec.:
SR 75 - 76 in 5 min 5 sec. (good rooms):
Lokarr and Mogdrogen are of course also doable 
Closing Statement:
The 1.2.1.2 Spec makes this guy quite tanky and very high dps. Have Fun!
. Phoenix devotion is used mostly for Fire builds, but fits here too. My build is squishier, has more RR thanks to Ill Omen, less flat Cold 
, but still comparable damage (in more skillful hands than mine). Because this topic build is pretty sturdy, it can facetank more and deal decent damage at the same time, so results are better. I would try this variant 