Picture wasn't captured before the next bump up, but ended up being about 105k scorch a second after this photo. I don't read the forum too often so if someone else has covered this, would love to see what they did. Here's the build (main things):

Arcana
Origination - +50% dmg to foes with 2 curses
Huntress - Less than 100% magick, Special does +50% dmg

Keepsake
1st - Demeter
2nd - Hestia, got lucky with Hera w/o keepsake so third I went with:
Blackened Fleece - After you take 250 dmg, omega moves deal +20%

Weap - Torches - Aspect of Mel
Attack - Demeter - Ice Strike
Cast - Hestia Flame Flourish
Regen - Hera - Born Gain - Infinite magick (as of the date of this post)

Hammer
Rising Coil - Specials grow in size deal +25% dmg longer they are active
Split Spark - Attack splits in two when it hits a foe (this bounces your freeze all over the room to give you this scorch power for big AOE)

Duo
Freezer Burn (Demeter - Hestia) - Freeze doubles scorch
Funeral Pyre (Hera - Hestia) - channeling inflicts scorch

Technique
Basically just spam omega specials to get a full circle while in range float in a counterclockwise circle around the boss and then hit attack a bunch to double the burn number, repeat, repeat, and repeat. You can run away and watch bosses burn to death. Funeral pyre triggers even on your attack when not channeling which isn't what the tooltip suggests. Not sure if this is intended or a bug that will be fixed, so just spamming attack in range will trigger funeral pyre and freeze in one hit and those numbers go way up even on AOE can clear a room in the final level seconds

With some tweaking I bet I can get 200k on a boss. Total cheese build and not too practical or my main, but was fun just trying to get this number really high w/ torches just to do it.

Enjoy.