Mandy's new Taboo has changed her enough to make it important to look at her in a new light. While she is still VERY strong, it is important to look at how Mandy's new mandatory 50 card deck pushes her from 'the combo queen' to a more toolbox focused Seeker.
Previously, at 30 cards in her deck, Mandy could churn through it absurdly fast and assemble pretty much any combo she wanted within a few turns. This was because Mandy could thin her deck absurdly fast early with the first part of her investigator ability, with most searches hitting 1/3rd or more of her deck and removing 1/15th of it resulting in her being able to do absurd things like assemble her Segments of Onyx within an average of fewer than 3 searches, or to find a copy of a specific card in her deck very consistently with OBOL around 50% of the time. This meant, in addition to being able to stay ridiculously gassed with the double draw of her ability, she also could create absurdly intricate combos within a very short timeframe that dominated the game.
At 50 cards though, that aspect of her has weakened. After crunching some numbers, the extra 20 cards in her deck doesn't hurt her that much, but the pain is noticeable. In regards to 9 card deep searches, Mandy will now need around 1 extra search to find a specific card she is searching for as often as old Mandy. This doesn't hold forever (as you draw through your deck the odds of finding the cards you want approach 1) but it holds for a fairly long time.
For example, at 10 cards deep into your deck, if you need X card with old Mandy your chance of finding it your first pull is around 76%, ignoring the chance of having drawn it before (which is both REALLY hard to summarize the math of, doesn't always reflect the reality of play because often times you want specific cards based on context anyway, and hurts new Mandy quite a lot, she is way less likely to have those cards in the initial 10), while with new Mandy its only 42% on the first pull and 44% on the second assuming you double drew, and 54% and 56% if you 'wide' draw, meaning about an 80% chance if your really digging. These are actually worse than even the initial odds for a 'generic' seeker who we assume only drew 5 cards into their deck, who has a 64% chance to pull the card, meaning that Mandy actually is now worse at finding specific copies of cards than a 'generic' seeker.
This isn't going to hurt her terribly on any individual search; its still safe to play Mandy when she needs to find maybe one or two specific cards, but Mandy no longer is going to be as good at making 'strict' combos where you need a bunch of specific options in specific orders, because those misses once you get to the 'middle' phase of building your combo and your 'hits' drop from 1/3rd of your deck to maybe 1/8th will add up. She is also worse at finding that specific card you want, and her ability to exploit cards like old book of lore late game has dramatically shifted away from using it as a 'finisher' to search for combo pieces once your deck gets thin, because your deck in a realistic game of Arkham, even with a relatively fast cycle strategy, just won't get thin enough where your able to assemble that combo in a timeframe its relevant: Mandy sure can get to the point where your old book of lore dig for 6 will find you a combo piece every turn... but a combo that takes till turn 7 or 8 to get started isn't really practical.
Mandy's niche now is that when she is searching for options with generalist tutors, she can more readily assemble a toolkit to handle future problems. Even in regards to situations where she can add in 'sidegrades' for a given option (ex: Tossing in "I've got a plan" to supplement Occult Invocation to have twice as many combat cards with not even twice as much deck) she doesn't actually find them much faster at many break points, but if you have a lot of interchangeable tools getting two options every tutor rather than one isn't even akin to doubling your draw, but also allows you to more effectively prep for specific events without distrupting your tutor as much: Sure you need to dig once more to find X in most situations, but now while your digging you can snag a combat event to let you snipe an enemy on a guardian autofail, or a shortcut to come in clutch on a 'race to the exit' scenario later.
There is also a more subtle change: Mandy now scales much less aggressively with XP, which also was a problem with her pre-taboo self, because she was so good at forcing XP cards to consistently enter your hand. Now, not only is she struggling to find XP cards as consistently, but because she is trying to run multiple 'sidegrade' copies of tools she wants to find, she has less XP to spread out overall, making Mandy have a lot of focus on the 'low level zoo' Seeker cards. She certainly can utilize big chunky cards, but Mandy probably will shine a bit better spreading her XP out more, and due to the fact her scaling is a bit awkward and her deck's overall XP density is inherently lower than other seeker's, with a lot of her value focused on level 0 situational 'magic bullet' cards like events, you might want to consider her as a 'replacement cluever' for late campaign character deaths.
In essence, Mandy is much less about overwhelming the scenario, and is far more a 'toolbox' character now who is fairly good at assembling multiple situational cards without slowing down her core strategy too much. She no longer is about assembling the Pendant of the Queen and keeping it infinitely charged with charge manipulation shenanigans (in fact, pendant has gone from one of her iconic cards to her probably being the worst seeker in the game at assembling it, though it isn't so bad you shouldn't ever consider it, because the fact its a 1 XP gamewinning tool that synergizes with your ability to pick up useful cards 'on the side' means the fact its slower and less consistent doesn't matter as much) so much as being the seeker who says 'I can handle that' pretty much every turn. She is a lot more scrappy and reactive because her payoff is now based on you thinking ahead to what you might need rather than power-looping your deck to repeatedly chain together combos or fast cycle out deduction+working a hunch and reshuffling every turn.
Overall, the Taboo is good in terms of reigning her in while keeping her a valid character. I doubt we have seen the end of Seeker degenerate combos, but its unlikely Mandy will be the one to do them from here on out. Harvey (who struggled in Mandy's shadow) now have a niche because of this new limitation. But new Mandy isn't bad in the slightest. The only real downside is that 50 card decks are a bit more awkward on collections and storage, but that isn't exactly the end of the world considering Taboos mostly exist for 'superusers' anyway.
