Review of my limited pool experiment
It's not about saving the world, it's about the things we learned along the way. Or something like that. ;)

I would like first to acknowledge this is a tiny sample. Running a single campaign with two investigators is statistically not significant to draw broad conclusions about limiting the card pool in Arkham Horror. However, this doesn't mean I haven't learned a few things along the way.
Different archetypes, different results
Kate Winthrop is a Seeker, this card pool is large and mainly focused on a single thing: getting clues. I had no issue finding interesting cards for her deck. Hank Samson is a Survivor. This card pool is a generalist rather than being specialized, it was much harder to strong cards for the goal of taking care of monsters. I would expect Seekers and Guardians to be less impacted by a limited pool than the other archetypes.
Signature abilities
A more generic signature ability like Hank, taking damage for others, hasn't been impacted by the limited pool as expected. Kate's signature ability is based on two categories of cards, Tools and Science. This was not an issue, Tools are numerous in the card pool and the Hemlock Vale investigator box had several cards dedicated to building on her signature ability. I expect to see more of this in the future, each investigator box containing cards to expand its investigator's abilities.
Experience point upgrades
This is one aspect I didn't originally think about. Until I went for familiar upgrades, I didn't pay too much attention to how the limited pool would also affect my deck upgrades. Probably not a big issue for decks with inherently few restrictions, Hank and Kate are two examples, but I could see this becoming an issue in a few cases, like for example, an investigator not having access to the five levels of his archetype.
Forcing you to use different cards
You could see this as a negative, but it's a positive for me. Limiting my pool forced me to look at different cards, rather than using the same staples over and over. That's already something I'm conscious of, I often try to use unusual cards to get out of my zone of comfort. Dr Charles West III is a good example. It's not a particularly strong card, I would rarely use it, but in this context, with Kate, it seemed to be fitting.
What other cards I would have used in my Hank deck?
I find the Pitchfork to be an awful card, but I had so few weapon options, I had to pick it. A Fire Axe or Meat Cleaver would have been much better. How about Peter Sylvestre to help mitigate sanity loss after switching form? A simple Scrapper could have been fun to spend all these resources I abundantly had. With a high fighting stat, some cards like Improvised Weapon can be useful in a Hank deck.
Looking at a few upgrades, I could myself having so much fun with a Chainsaw. Granny Orne is a good soak and can help mitigate encounter card effects by providing more willpower. Brute Force is a classic for fighting Survivors.
What other cards I would have used in my Kate deck?
Fingerprint Kit from day one? Heck yeah! The Hawk-Eye Folding Camera is a good Tool to have. Laboratory Assistant would have had some considerations. I like having "I've got a plan!" in a two-players game, it's a practical option to have if your cluer suddenly needs to fight.
In the upgrades, I dearly missed Deduction, it's far too powerful to skip. An upgraded Perception, maybe? Since her signature ability is new, many cards from the Hemlock Vale pack were made with her in mind, and therefore I don't think I would have made many changes in the deck.
Overall, I had a lot of fun running this experiment. It forced me to think differently about my deck building and I appreciate it. Deck building is one of my favorite aspects of Arkham, anything that can get my creative juices flowing is welcome. The campaign didn't feel overwhelming because of the card pool limitations. It is worth mentioning I usually play on easy/standard, things could be radically different on hard. I might run another experiment like this in the future, or maybe run a comparison between two decks as a thought exercise, I haven't decided yet. Replayability is part of the charm of this game.