Hello, my siblings in the art of the occult o/
I was looking at the plethora of curses that are being introduced this Wednesday; more specifically, Penance.
The node from Profane Veil’s skill tree that allows you to apply Penance reads:
Penance deal [5%] more damage per 1% of Damage Reflected.
Given the wording, it looks to me like the percentage of damage reflected used to calculate that damage scaling is that of the player who applied the curse.
However, regardless of whether I am right in that assumption or not (and if I’m not, I suppose the rest of this post is superfluous :p), I feel like having that scaling based on the percentage of damage reflected of the player who takes the hit that triggers Penance’s damage would make it a lot more interesting.
It would still allow daring Warlocks to invest in reflected damage themselves and throw themselves at their enemies. It would allow Acolytes to invest in different sources of damage reflected for their skeleton friends, and throw them at their enemies. And, perhaps most importantly, it would allow weirdos like my friends and I to use Penance as an “external” piece of a Sentinel retaliation build (or, even in less extreme cases, to make Penance work better when played with a party member who plays melee and invests any non-zero amount of build resources in retaliation).
I know we’re very close to release, so if I’m right in assuming this isn’t how Penance scales yet, I’m of course not expecting any change before release; but I thought I’d mention that here, in case it ends up falling upon the right set of ears. 
Thanks for reading! I’m going back to obsessing over my 48th Warlock planner ^^