Fire Crash, The New Flame Blast

The idea here is to take one big swing and then watch the world burn. The primary mechanisms at play are:

Ice Crash - excels at delivering single large hits, which is how ignite has to be optimized. Ice Crash is balanced around not being able to be supported with multistrike, which is why it delivers massive damage but at a slower pace than most other melee skills.

Herald of Ash - for massive ignites in packs or against bosses that can be lured in range of weak monsters.

Fire conversion - via the newly improved Cold to Fire Gem and Avatar of Fire.

Staff - for the crit and for tree synergy. It can be done non crit. The animation on a Marohi Erqi for a build similar to this is pretty epic.

Elemental Prolif - Supporting Herald of Ash. This is where your pack clearing comes from and it is arguably more effective than swapping Conc Effect for Inc Aoe. You have to play around the corpses correctly, but you can take down map bosses just by dragging them through prolif corpses that are burning for some ridiculous DPS number that I'm not going to bother to calculate.

Elemental Reflect will kill you. Yes, even a single rare with elemental reflect will kill you if you crit. You work around this by burning them to death with HoA Prolif

No charges
Charges + Onslaught

Assuming you hit a mob with 1 Hp remaining for the maximum amount
49136 (maximum base damage-1) x 5.57 (crit multi) x 1.37 (HoA) x .8 (Prolif) x 4.98 (fire/ele + burn damage from tree x 2) x .2 (burning) = Something like 50k Dps. That seems low based on how fast things die from the prolif. Maybe that's because I ignored resistances. Whatever, I tried.

Alternative helm:
If I had a 6L Cloak of Flame or a 6L hege's, I would use Cloak of Flame. The build is pretty squishy and it's melee and it has to stand still for a while to attack. PoE isn't forgiving of any of these features.

6L - Ice Crash + Conc Effect + Cold to Fire + Melee Physical + Fire Pen + WED - You can put Added Fire in for Fire Pen if you want to sit in town and jerk off to your DPS numbers
3L - HoA - Inc AOE - Prolif - Basically the build right here.
3L - Faster Attacks - Leap Slam - Fortify - Every melee uses this
4L - CWDT - Blood Rage - Ice Golem - Ele Weakness - I'm lazy

28 Sep - swapped Inc AOE for Fire pen on the HoA Link. Apparently Fire Pen does not support HoA. Thank you reddit user u/battled
29 Sep - Added alternative helm Alpha's Howl, which is required to use Inc AOE on HoA with my current tree. Updated tree as I had significantly undervalued AOE on my original tree. Thank you reddit user u/BioSemantics

Sorry they're so short. I can't seem to get FRAPS to record for more than 30 seconds.https://youtu.be/PycvWijyx44
https://youtu.be/3KmVzdjWCTU