I've been playing a
first life blaster warlock. I've taken it through R1 raids and enough low skull reapers to get 24 reaper points, and it's performed reasonably well. The built-in Legendary Affirmation from the staff provides a huge survivability boost on top of the Warlock's other temp health abilities. Ruin and Greater Ruin excel at deleting reapers.
The build assumes minimum Epic Destiny AP (53), and assumes no racial or universal AP tomes.
There's a complete breakdown of spellpower, crit chance and damage sources in the build doc. Summary (outside of reaper, does not include Wellspring of Power):
868 Fire Spellpower
054 Fire Spell Crit Chance
175 Fire Spell Crit Damage
801 Radiance Spellpower
052 Radiance Spell Crit Chance
145 Radiance Spell Crit Damage
741 Force Spellpower
051 Force Spell Crit Chance
115 Force Spell Crit Damage
745 Positive Spellpower
051 Positive Spell Crit Chance
115 Positive Spell Crit Damage
100 Evocation DC (includes target debuffs)
I've included past life prioritization as well, if you choose to play this build long-term. There's plenty of growth potential with a whopping 82 Universal Spellpower still to gain from reaper points and the Touch of Power augment set.
My only complaints about Warlock are the same as Eldritch Knight and Pale Master: Damage immunity stripping. Tiefling Ash does not last long enough, especially on red or purple named that are immune to (or worse, healed by) fire. Hopefully we'll see damage immunity stripping as a core mechanic of the Cursekeeper epic destiny tree, whenever that is released. Warlock desperately needs it to get rid of that frustrating aspect of the build, because not using an epic strike and turning off pact dice for mobs healed by fire feels bad.