Open question, as of version 0.61:
I'm having trouble balancing Forsaken with Archer's Shot.
Currently, when used by an unbuffed Mage against an average (30 SPC) enemy, Forsaken inflicts 30 points of Defense reduction, or 30 extra points of damage per hit for 5 rounds. This isn't actually much better than Rogue's Below the Belt, which currently inflicts 23 points of Defense reduction against the same, and it has to compete with Indignant Variati, which costs the same. Against an average (30 DEF) enemy, Indignant Variati inflicts an immediate 330 damage; you would have to make over 11 attacks in 5 rounds to make Forsaken the superior option.
Normally I would just make it stronger, buuut things get screwy with Archer's Shot. At its upper bound it hits 10 times, meaning every point of Defense reduction equals 10 extra points of damage. Against an enemy with 0 Defense (the result of using Forsaken on an average enemy) it inflicts 585 damage (!) even without Attack buffs. And this is without even getting into using Special buffs, or stacking Defense debuffs with Forsaken to reach negative Defense. Against an average enemy, Witch's Forsaken inflicts 45 points of Defense reduction, which translates to -15 Defense, which translates to 735 damage (one-shot kill territory!!) with a 10-point Shot.
In effect, this makes Forsaken pretty much useless unless you stack it with other debuffs or use the upper bounds of Archer's Shot, which makes it extremely situational compared to Indignant Variati or Perdition, which require far less setup to accomplish similar results.
I can't fix this by reducing the weight on Shot, because the core problem is the massive variance resulting from Defense changes, which is inherent to the multiple hits. If I balance Forsaken for regular attacks, Shot's potential becomes gamebreaking; if I balance Forsaken for Shot, Forsaken becomes useless with regular attacks.
I figure I've just designed myself into a corner and I have to accept that; creating a 10-hit attack was always a risky idea that I knew was going to run up against the limits of the battle system. I mean, maybe this is okay? It's not like it's easy to get Archer up to 10 points; maybe it's alright to let players break the game if they're clever and determined enough to pull off this combo?