Warlock party buff Soulburn

[Quu]

Warlock party buff soulburn was not applying to my party yesterday while farming terrors, blackwyrm. Can anyone elaborate why?

We tried to wait for the debuff to finish had 3 warlocks - not a single one could apply the soulburn effect(one time i tried, next time other, even waited 10minutes  between applying buff). The thrall would just explode and the skill would go on CD with a debuff, but not buff... Another strange effect - noticed, that terrors aoe damage was not applying while with warlocks debuff.... ( maybe some other bug but i dunno).

Only happening while fighting terrors, blackwyrm. For example i moved channel, was alone and it applied perfectly... whats the deal?

[Quu]

so there's no advice? :/ how to avoid it