You give an opposing figure up to three -1s for one attack roll after the roll has been made and accepted (meaning AFTER all the probs are done so they can't prob it later). For each -1 you gave them, they get Hex Tokens which can be redeemed for a +1 to a friendly character's attack as a free action. Since you can't be given more than one free action a turn for a single effect, they can only remove the tokens one at a time. As long as you're just doing this to a single guy, he's getting tokens almost three times faster than he's spending them. If you spread this effect to multiple guys though, it waters the effect down because they could each pool the +1s onto a single figure to try and overcome the negs. So you focus on completely blocking one guy, until he dies and all of his tokens are lost, and then you move to blocking the next guy (ideally). Also, since this isn't a unique, you could play multiples of her, and give someone up to a -6, -9, or even -12 to their roll in a 300 point game. Since it's affecting the roll and not the combat value, the rule of three doesn't apply. Toss in that she doesn't need LoF and a lot of people aren't going to want to be anywhere near her range.

Worth noting that any remaining tokens have no effect on future attack roles but provide free faux perplex too.

She's not being watch-listed because she's "broken", she's being watch-listed for the sheer number of times she makes your opponent want to punch you in the face after you've "HEXED" his 21 attack to an 18 attack (thus missing your 19 defense).

Upside of her defence power is that it still does unavoidable damage, making it oddly better than current mystics.