Hello,
I’ve noticed something that seems to be an inconsistent behavior with the above mentioned skill. More precisely if the boss rotates or moves and the position from which the skill was used no longer faces the back indicator subsequent attacks no longer benefit from the back modifiers. However, this doesn’t seem to happen the other way around (if you don’t start using the skill facing the back indicator no attacks will benefit from the back modifiers no matter how the boss rotates or positions afterwards) which makes predictive playing in this particular case not possible and also causes some dps loss.
Was unable to replicate the same with similar back type skills that do damage over a period of time through multiple attacks such as Berzerker’s Dark / Bloody Rush or some of the Reaper’s Swoop skills.