Herald of Ash overkill damage cap?

Hi, I'm doing the same build I was doing in March during prechia league.
It revolves around killing worms with discharge and applying a big burn with Herald of ash.

But when you increase the damage of the discharge to much, not sure what the breakpoint is. The burn stops dealing damage at all.

I was not able to test if this was a problem by hitting some kind of dot cap, but I'm pretty sure this problem lies in the overkill damage.

As the current build has a lot less dot damage then the previous iteration. But it has more on hit damage then before.

This is the old link and it has some showcases of the bug that are still relevant: https://www.pathofexile.com/forum/view-thread/3736041

I'm a little sad due to the fact I did a cool ass craft for the build already that cost me quite a lot of money. And there is not really any other fitting build for this item.