
I've been playing Olive in a Jim deck for Carcosa, and...my experience hasn't been very good.
The numbers on the card are the best parts. 2 resources for 3 Horror soak is great. But I don't think that's worth the slot on its own, as Mystics traditionally have lots of options for Horror mitigation.
Her ability is underwhelming. On standard difficulty, you're likely to draw something like (-1), (-2), . "Great!" you think, "I avoided the tablet!" But, because of how math works, you've drawn a -3 instead. So what? You just have to commit cards or whatever until you're 3-up or 4-up on the difficulty. Well, why not just draw a single token if you're 4-up on the test?
My beef with Olive is this: in order to use her, you have to compensate for the moderate negative value you're likely to draw, but by doing so, you no longer have a statistical advantage by using her.
Now, she combos pretty well with Song of the Dead and Defiance(2). But now you've got a combo piece in your deck that doesn't do much on her own except offer Horror soak. And you're unable to play other allies like Arcane Initiate, Peter Sylvestre, or David Renfield.
The Jim deck I've been playing beats tests because it has 3 extra (0)s in the bag (the ). I can essentially under-commit on tests because I'm likely to succeed at 2-up or even 1-up. Using Olive actually requires me to commit more to my tests than I would otherwise. So it's only helpful when I'm using Song of the Dead, but then it's only 1/turn, and even then it's far from guaranteed to draw that .
The best case use I can see for the witch who'll try anything once is in conjunction with Lucky!, as that allows you to react to the swingy-ness of the double token draw. You drew (-2), (-3), ? Well, you were only 3-up on the test, but you can succeed anyway! But then again, isn't that just a testament to how good Lucky is?