Infinite Vaal Volcanic Fissure with Over 150M DPS in 3.21 Crucible League
To Preface, here is my build killing Feared on 150M+ DPS set up.
In 3.21 league, we were introduced with the mod"Vaal Volcanic Fissure and Vaal Molten Strike have 80% reduced Soul Gain Prevention Duration"This mod is available in One-handed melee weapon, Two-handed melee weapon, and Shield.However, league only unique, EL'Abin's Visage is also considered shield.So, we can achieve 120% reduced soul gain prevention on vaal volcanic fissure using both weapon slot and helmet slot. Opening possibility of infinite vaal volcanic fissure to ALL ascendancy classes as it does not require soul catcher flask.
With soul gain prevention time being 0 second, we still need to provide soul cost.However, we can bypass the soul cost with rage cost using Hateforge glove.Also in combination with Rotblood, Chain of Emancipation, and Lethal Pride - Akoya (Chainbreaker), we can keep the rage up at maximum letting us spam vaal volcanic fissure.
Vaal Volcanic Fissure has very large scaling compared to other skills as it scales with projectiles while not having the 50% less damage with projectile compared to original volcanic fissure or vaal molten strike. It provides large sum of damage with minimal investment. Furthermore, Vaal Volcanic Fissure is also an auto aim, auto target skill, which is very relaxing to play for both map and boss.
From my experiments last few days, here is what I found on how to scale the build.
1. Area of Effect
If you increase area of effect on your volcanic fissure, you increase both the spread distance of the magma balls and the explosion radius. It is similar way to molten strike.
For single target purpose, we want to reduce the AoE so that explosion is still decent sized while keeping projectile travel distance short to get full benefit of point blank keystone.
For bossing, we want to use anomalous concentrated effect for 40% less AoE and blood stand for extra 5% less AoE.
2. Projectile Speed
Unlike molten strike which increases travel distance with projectile speed, projectile speed only affects the speed on which the magma balls drop. So getting more projectile speed only benefits us by increasing the speed the damage occurs.
3. Attack Speed
Resulting attack speed on Vaal volcanic fissure is highly related to the speed which the magma balls drop and fissure travel. Higher the attack speed, faster the fissure movement.
4. Action Speed
Similar to attack speed, increasing or decreasing action speed also works multiplicative to the fissures travel speed and magma balls dropping speed.
5. Vengeance Cascade
Vaal volcanic fissures attacks are attack projectile. So using vengeance cascade will make the balls bounce back to the origin of the balls departure which is the fissure doubling our damage. Also, for sake of point blank, the magma balls travel only vertically which means we always get the full benefit of the point blank 30% more damage.
For DPS Calculation with vegeance cascade,
(Average Magma ball hit damage) * (Attack Rate) * (Ball Count) * 2
In my case, I have 2.4M hit, 3.44 attacks per second, and 12 balls. Resulting 198M DPS.
However, this is the minimum dps as the fissures can travel back to the single target and perform extra attacks. So in game, it is usually 20~50% higher than this number.
Here is my current PoB.https://pobb.in/5xCNsSiuQLVt
Here is a T16 mapping Video for who are interested in it's mapping potential
I have wrote little more detailed guide on the forum
https://www.pathofexile.com/forum/view-thread/3378579
which may answer more of your questions.