GrimTools: Pyromancer, Level 100 (GD 1.1.9.8) - Grim Dawn Build Calculator
Whooh! This patch gave the ol’ 2h retaliation mage a buff, and it is FUN. Want to feel like an unstoppable, immortal spellcaster, decimating their enemies by the masses, with beautiful spell effects reaching across the screen? LOOK NO FURTHER (but actually do also look further, there’re a tonne of great builds around, BUT MAYBE THIS IS ONE OF THEM).
This is an elemental 2he retaliation caster pyromancer, and it feels exactly like a powerful pyromancer should The damage is devastating, but the build is also incredibly tanky.
Damage
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Retaliation damage and On-Hit effects
With all buffs up, this build has ~194,500 elemental retaliation. The highest damage so far after 100-170 of Crucible is ~440,000 damage which seems about what it should be with the elemental/fire RR available to the build. When hit, additional retaliation attacks can trigger: Ulzuin’s Wrath (15%), Wave of Fire x2 (10% each), Hyrian’s Glare (35%) for a combined total of an additional 70% retaliation damage on top of what they take from the initial hit. While this won’t trigger on every hit received of course, it does make for some nice spike damage when taking the first hit in a fight, or helps to deal retaliation damage to ranged or caster enemies. -
Retaliation Attacks and On-Attack effects
This build is built to stack retaliation damage added to attack. It’s primary attack is Dreeg’s Evil Eye, with 30% retaliation damage added to attack and a bonus crit damage of 69%. It’s common to critically hit for ~200k damage per DEE hit. Sigil of Consumption has an additional 22% retaliation damage added to attack, and can stack for quite a bit of damage. Dreeg’s Wounds on the movement augment has 40% retaliation damage added to attack in a 5 meter area, good for small AOE crowds. There are a number of other retaliation-added-to-attack triggers which contribute to the damage: Pyroclasm (10% x3 projectiles), Rain of Fire (6% per projectile), Dawnshard x2 (6% each).
To help with damage, Flashbang reduces enemy DA by 280.
Note - In this build I yolo’d with some OA prefixes on all of the green items which of course, helps substantially. But I believe that with Flashbang’s debuff, this build still will function well without.
Tankiness
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Damage mitigation:
15% Damage absorption from Possession with 25% reduced target’s damage from Ulzuin’s Wrath, while offering 25% fumble and impaired aim to enemies from Searing Light significantly reduces incoming damage. I know, fumble seems like a strange choice for a retaliation build, but in this case I feel like it allows the build to facetank multiple nemesis bosses at once without feeling too precarious. The build comes with Phoenix Fire for 168 damage absorption, plus 660 from Blast Shield and 130 from Prismatic Rage should your HP dip for a moment, acting as a great failsafe during spike damage. -
Healing
The build comes with a tonne of healing - Sigil of Consumption, Dreeg’s Evil Eye and Ulzuin’s Wrath each have retaliation damage added to their attack, and each convert some of that damage to health. Ulzuin’s Wrath can hit 7 targets per 1.5 seconds, and the AOE lifesteal from this is significant and generous. Sigil of Consumption has 22% retaliation damage on it, and heals for 30% of that. It can be stacked, and with it’s 5.1 meter radius, it can also deal damage to a group of enemies, healing you for all of it. Dreeg’s Evil Eye has 30% retaliation and 8% attack damage converted to health. DEE is the primary attack of the build, and it’s healing is plentiful. Lastly, Blood of Dreeg serves as a nice extra heal when you need it.
To help with tankiness, this build comes with a wide range of stuns, knockdowns and confuses, helping to stagger incoming damage in big crowded fights.
Crucible 140-150 without crucible buffs:
As you can see in this video, even without the crucible buff assistance, doing Crucible feels like a breeze. Blast Shield only triggers twice within the entire fight here, meaning that at only two points from 140-150 did the HP drop below 60% for a moment.
Crucible 160-170 with buffs:
I didn’t try Crucible 150-170 without crucible buffs yet, but I imagine it’s quite possible, although the playstyle may be more defensive. Still, with crucible buffs you can see that majority of the playstyle involves facetanking to maximise the retaliation damage, and explicitly dodging to avoid debuffs or spike damage from specific nemesis’.
So if you want a tanky, comfortable, self-healing, hard to kill, highly damaging spellcaster with a lot of AOE effects and damage, have fun with this build. 
Enjoy~