Herald of Thunder + Energy shield on hit

Hello dear reader,

CONTEXT:
I'm currently working on a "Herald of thunder" build and the different ways to get defences. The build I'm using have some energy shield which is completely lost since i'm using "Storm Secret" unique ring (thus inflicting self damage).

BUG:
I decided to put this energy shield amount to some good use thanks to "Discipline" aura coupled with a "Watcher's Eye" mod: "Gain 29 Energy shield per enemy hit while affected by Discipline".
The bug is here. This mod doesn't work with herald of thunder.

REASONING STEP BY STEP:
I know "Herald of Thunder" is not a spell and everything. I know HoT does hit. I have read the mod ten times and I'm sure of it, it should count for HoT.
I do have "Discipline" since I tested this without "Lone Messenger".
I do have A LOT of defence, so the 250 lightning damage from "Storm Secret" result in something between "16-20" effective damage per ticks (meaning I should regen energy shield for every tick).
Also, while hitting with spells ("Shock Nova"), I do get energy shield from the "Watcher's Eye" mod.

Can any dev help me on the matter please ?
Thanks for your work !