Poison bomb, no dmg when stunned?

[fozian]

I just noticed in HC nighthold that my poison bomb did no dmg when I was stunned??
It was the trash between spellblade and krosus, the big packs that uses some stun. My posion bomb procced right before I got stunned. And for some reason it did no dmg at all. Is this a bug, and how does it work in pvp? Does it do 0 dmg when stunned in pvp too?

Seems to be the same case when you die.