Jacqueline, while less specialized than other Mystics, can be quite a powerful investigator who's ability interacts in strange and beautiful ways with so many of the mystic cards we know and love. I also appreciate her 6 Health and 9 Sanity which makes her quite a bit tankier than one might first expect, especially once she's put on her nice fancy Robes of Endless Night.

STATS:

5 Willpower - What you really want in a mystic. Such a high starting value in your primary stat makes you so much less dependent committing cards when facing encounter cards and casting your spells.

3 Intellect - Good but not great clue finding. Throw in a few flashlights and/or perceptions and Jacqueline can help gather a clue or two while saving her arcane slots for fighting spells if you decide to go that direction.

2 Combat - Don't expect to win a fight without a shriveling or azure flame ready to go.

2 Speed - Also don't expect to go passing encounter speed test or evasions anytime soon. This is what mystics bring deny existence and ward of protection for.

Overall I really like her stat distribution. Good support clue-finding and excellent willpower for all the normal mystic shenanigans. Her biggest detriment is the inability to deal with monsters without any assets or events.

ABILITY:

I'd categorize her ability as having separate purposes that interact with either her own cards, or her fellow investigators.

With her own cards, her ability makes token flipping cards much more reliable. Improve the resource gain on Voice of Ra, proc cards that want tokens to be flipped like hypnotic gaze, or dodge self-damaging effects on cards like storm of spirits or shriveling. Additionally it becomes that much easier to gain additional cards through prescient and crystal pendulum. You can include cards like Olive, Premonition, or Scrying Mirror to support the token flipping reliability but I've found Jacqueline's ability was strong enough that it didn't require additional support.

When using her ability in a group, look for where success is needed and aim to end (or start) your turn there since you have to be on the same location as the investigator flipping the tokens. When assisting friends there are two instances in which i found her ability worked best, tests with a narrow chance of success (starting at +0 or +1) or tests you can't afford to get the autofail. For the former can increase the odds of finding a 0, +1, or Elder Sign and has surprisingly often passed tests that had no right to pass (note* I haven't done a full mathematical analysis on her token flipping odds, although I would love to and might in the future). For the latter, there are some tests that you JUST. CAN'T. FAIL. With Jacqueline you can more reliably dump all your cards into this important test knowing that even if you do flip the autofail you can cancel it. However this does create a new range of negative tokens in the bag to consider, for example flipping the autofail, the -5 and the -3 means the test is now a -8. There is an excellent analysis of this for the Olive McBride card and I suggest you read more up on it there, however anything that lets you guarantee dodge the autofail token is worth noting.

Her ability can be summarized by the word Reliable. Seeing the future is never a guarantee. But once per round, on one test or token flip, you can breath a little easier.

UNIQUE CARD and WEAKNESS:

Arbiter of Fates is cool, simple, doesn't take up an asset slot, and simply doubles her ability usage every turn. Great. Refer above to why her ability is nice to have in your pocket, now you have it twice and you don't have to feel so bad about using it to dodge a nasty encounter card. Pretty unnecessary for solo as you will be using your actions to play cards or move around more often but can be nice if you have the time and resources to slap it down.

Dark Future is also cool, simple, and just sucks to have out. Quashes all the benefit of Jacqueline's ability minus niche cases like Hypnotic Gaze or Voice of Ra where you want to draw tokens. It even spitefully turns off your ability to cancel the elder sign for cards. However, since you now won't be using your ability on tests, you now get to use it on this jerk of a card at the end of each of your turns in hopes the helpful blue token will appear and save you. Her weakness has both an extremely notable upside and downside. On one hand it does not require any action to deal with, it will simply go away on its own. On the otherhand... IF it ever goes away. Some missions you will end every turn, flip your 5 (or 7) tokens, and audibly sigh as you realize there's nothing else you can do to help speed the process along as you remain ability-less another round.

SHORT NOTE ON DECK BUILDING:

Although Jacqueline has a very limited card selection range, the way she interacts with mystic cards makes many more card options viable. Voice of Ra and Crystal Pendulum I would consider core to her, as they provide the resources and cards and Willpower boost that fuel her primary actions. If your deck utilizes lots of event spells, prescient is a reliable way to pull cards from the bin. Again, just look at every card that relies (or avoids) tokens in some manner and consider that Jacqueline now has an addition way to interact with these archetypes.

PS. Take 2 copies of Arcane Research if you feel like being a mad lad. Watch your friends get jealous as you get 2 additional xp each scenario and ascend to maximum wizard.

CONCLUSION:

In the end her ability doesn't need to support a janky archtype (although it can, and does), instead your deck can also be "Mystic Goodstuff" with a powerful supporting ability for the team, and thats what I really like about her. Her ability will always be useful, it will have you discussing with your team each round where you should use it and where you need to be to help out. Its fun, cooperative, and powerful. If you made it to this part, I really suggest you try out Jacqueline Fine and see what its like to see the future and have (a bit more) control over chaos.

For those interested in detailed probabilities, here is what I have computed, and the comparison with a default investigator. The bag I use is the following: [+1 (elder sign), +1, 0, 0, -1, -1, -1, -2, -2, -3, -3, -4, -4, AUTO_FAIL];

The "cum. prob" is the probability to have a result higher or equal to the given value.

So Jacquelines offers a nice bonus probability on everything.

I think Jacqueline is an enjoyably straightforward character. Her limited card selection isn't that bad since most of the spellcasting decks I make are very heavy on Mystic cards anyways, and having the 3 for her intellect is the best secondary statistic for a Mystic.

I ran a mathematical evaluation of her special ability (arbitrarily assuming the value of tokens in the bag was +1, +1, 0, 0, -1, -1, -2, -2, -2, -3, -3, -4, -4, -5, auto-fail), and how it compares to just having a flat skill bonus:

1. If the check is beyond her skill level completely, obviously her power is useless and you would be better off with a real skill bonus.
2. If the test is doable, but challenging, that is where her power really shines and becomes very useful. Her power never becomes as useful for succeeding as a flat +2 skill bonus, but it gets close (and it could be better if your goal is to avoid drawing a specific chaos token at all costs).
3. When the test difficulty drops to the point where it would be quite easy without her power, with only a few tokens in the bag that can fail, her power starts to become less useful. If the only way you could fail normally is by drawing the tentacles token, her power is barely useful at all. There are likely to be token distributions which cause her power to actually increase the chance of failure, but that did not happen with my sample token bag (her power was still a slight net positive, the triple chance of drawing the auto-fail was fully compensated by the excellent probability of succeeding even if she does).
4. When the test becomes even easier, her power then starts to become useful again. It is possible for Jacqueline to reach a point where she is so skilled that there is zero chance of failure, something which no fixed skill bonus can ever achieve.

Notice that Jacqueline can cancel Frost Tokens without resolving the "On Reveal" effect.

FAQs (taken from the official FAQ or FFG's responses to the official rules question form):

When a token is 'cancelled' or 'ignored' in its entirety (such as through Wendy Adams's ability, playing Counterspell or revealing two tokens with Grotesque Statue's ability), treat the token as if it had never been revealed at all. All of the token's effects are cancelled or ignored, and any effects that would trigger off that type of chaos token (like Baseball Bat with and ) do not trigger. However, when a token is only partially ignored or cancelled, as with Defiance, the token is still considered to have been revealed, and effects that trigger off it being revealed do trigger.

(From arkhamdb.com)

I played Jacqueline through hard on the circle undone, paired with Winnifred. And once you understand the keyword “revealed“, she is a truly wonderful investigator.

What’s amazing about her is that she plays completely differently from every other character and every other mystic. With other characters, you have risk mitigation, knowing that there’s a lot of bad in the chaos bag. If you are a survivor, and you spend the XP, you can get around it, but otherwise the only way to succeed is to go testless.

Now, the odds are in your favor. And with her new accessory and hand mirror, you can do even better. Rogues will be your best friends, Because now you can tell them the exact number they need to hit for Gregory, double or nothing, watch this, or Parallel O’Toole’s power. (Just the mirror by itself is a wonderful pick for Sefina.)

When Jacqueline isn’t around, you’ll miss her. Her ability means that your allies are more likely to survive the mythos phase & land attacks. Like all mystics, she could switch between offense or defense depending on what style she slots, or go with events that she recovers with prescient.

Who saw it coming?