This item added to FoA looks crazy Ember'thil, the Sun Blade - Legendary Two-Handed Sword - Grim Dawn Item Database
Huge skill bonuses to demo and occultist. The only issue i see… is that this class has 0 weapon pool skills! I guess you could throw on Seal of the Void, but that is just one. Is missing out on wps going to be worth it? I really want to make this sword work since it looks sick and ive never build a pyromancer before
It would be similar to a blade arc spam build + seal of the void proc 
Be aware that the arc/+targets mod to Fire Strike from the sword is pretty powerful itself and it gets added to a Seal of the Void if you choose to use that. That means the Burning Void proc hits 6 targets in a 240 degree arc - pretty sweet! Yes, it’s only 16% of the time though… although the regular hits are pretty solid too!
Plus the sword fully converts all the flat Chaos from Brimstone so FS really hits hard here. Focus on Health Regen and some ADctH and you’re all set. Enjoy! 
Currently just hit level 94 to use this bad boy, and while it does look good on paper, i must say that a default attack build with only one wps feels kinda terrible lol. No fancy animations or crunchy sounds, just the same two swing animations. I kinda wish the proc on the weapon was a wps instead
Im heavily considering just swapping to Darkblaze set for a twinge of dopamine
Have you found this item yet? Mythical Sigil of the Infinites - Legendary Medal - Grim Dawn Item Database
Adds elemental damage and another 25% chance WPS. That gives you at least 41% total with Seal of the Void. With an explosive strike bonus it looks like a good choice.
The only other possibility for 2 handed melee I can find is this thing Mythical Brawler's Gloves - Epic Gloves - Grim Dawn Item Database but honestly that doesn’t suit this build at all.
The final option would of course be to use the sword with a different class. But then the sword goes from “crazy” to “pretty decent.” But maybe that was intended: quite likely the stats are this good BECAUSE it’s hard to make an auto-attacking pyromancer.
Afanasenkov did it.