This is something me and a friend have been experiencing for about 2 weeks now. Essentially, Hawkmoon's Paracausal Shots aren't doing additional damage per charge as one would expect.
We just tried in a private match and had variants where;
Paracausal 1x through 7x dealt only 91 damage total
A non-paracausal shot insta-killed (on charge 2x but it wasn't the last bullet in the mag)
Paracausal 6x did 93 damage
The gun's SFX proc'd on all 3 last shots
Hoping Bungie acknowledges this, as it makes the gun much less enjoyable to use. It's basically useless right now as a result of all this.