I think this card is a fair sight more powerful than existing reviews give it credit for.
There are not many cards that grant two clues without demanding a skill test. The best examples in each faction as far as I'm concerned are Scene of the Crime, Connect the Dots, Intel Report, Drawn to the Flame, and "Look what I found!", but all of these are somewhat conditional or costly. Yet, despite their limitations, these are all great cards, well worth taking in decks that can support or set them up. Getting two clues without a test is fantastic, with the notable exception of playing solo where many locations have only 1 per investigator clues.
Excepting Drawn to the Flame, Stirring Up Trouble blows all of the above out the water when it comes to set-up cost. It's zero resources, and you must have Curse tokens available equal to your location's shroud. This is absolutely trivial. No enemies, no skill test, and completely resource free. If you ask me, this is a phenomenal advantage over its in-faction competition, Connect the Dots. I think this advantage is even strong enough to make up for the fact you have to spend experience to include Stirring Up Trouble in your deck. Level one cards tend to be fairly easy to purchase between scenarios unless you absolutely must save experience for a super weapon or Exceptional card.
Let's compare Stirring Up Trouble more closely to Drawn to the Flame. Both are free and zero set up save for the moderately costly punishment you take for playing them. The big difference is that even four Curse tokens is generally a much milder punishment than drawing an encounter card. Treacheries and enemies can take the better part of entire turns to deal with, or even cost an entire game round - and even drawing an additional mild treachery puts you closer to drawing the next awful one than you would have been had you not played Drawn to the Flame. After playing Stirring Up Trouble, you might not even draw all the Curse tokens you added before the scenario ends. Nothing bad happens to you at the moment you play Stirring Up Trouble - all the cost is deferred to future skill tests, of which there will be very few if you use Stirring Up Trouble to clear an objective location at the end of a scenario.
The other big point in Stirring Up Trouble's favor is that you might actively want at least some Curse tokens in the chaos bag, making its only cost into an upside. In particular, Curse tokens enable the additional effects of the cycle of Mystic spells in the same pack - Armageddon, Eye of Chaos, and Shroud of Shadows, and I think this will be a strong pick for Luke Robinson along with Blasphemous Covenant to make your first Curse token each round into an actually positive pull. This might be a narrower enabler than a card like Deep Knowledge, but it is likely a more powerful one. I think most decks reaching for Stirring Up Trouble will have some play for Curse tokens, but I actually don't think the tokens are so awful as to necessitate that. At least some of the times you draw a Curse token are during tests you would have failed or you end up succeeding anyway. And if not, well that feels bad, but just suck it up and be happy with your testless clues!
I'm not about to swap Working a Hunch for this, but then Stirring Up Trouble is quite a different beast. Working a Hunch is particularly good to finish off a location you were able to investigate once already, whereas Strinning Up Trouble will let you grab some clues even when you're not set up to investigate, or doing so would be prohibitively costly for some reason. This means it could also see play in the other present "off-class" Seeker Roland Banks, who appreciates this card's zero resource cost a lot. Finally, it is worth noting that this card does get a little weaker the more teammates you have past the first; more players means more future skill tests even toward the end of a scenario, and the two clues you discover will be a smaller proportion of those you need to clear a location or complete a clue-related objective. In big games, I might stick to other options without the endorsement of my teammates and some good Curse mitigation.