I think this is where folk are slipping up: Thaumaturge isn't a "research it until I find a way to kill it," class, as much as it's an "I believe I can kill it, based on the stories I've internalized and I will prove that they are true" class. That's where Charisma comes in.
Untrained/Clever Improviser are a thing. A bit of forewarning from the GM wrt the kinds of enemies the campaign centers on should be expected and encouraged. I would contend that Thaumaturges aren't MAD in so much as they aren't a do-everything class. A case could be made for gating the class to initially 2ish starting Recall Knowledge skills, so that the free skill increases feel more useful, but it really depends on the kind of adventure you're participating in, considering how under-utilized free Lore skills are, IMHO.
Luigi Lizza wrote:
You can kind of already do this in game through Magaambyan Attendant Archetype. Also, each Deity in the game grants access to out of tradition spells, as do the intersections of Witch Patrons and Lessons. It's hardly unbounded.
Witch seems like a better fit, imho, despite the familiar. Gaining power by trucking with higher powers seems to be his bailiwick.
I hate to be that person, but,IMHO, a Key Ability is there to explain how a given class does what it does, not determine what it's best at. I interpret the Thaumaturge as someone that leans heavily on the courage of their convictions, right or wrong, and that translates well into relying on Charisma to get things done. Find Flaws is less about encyclopedic knowledge of creatures or keen observation, and more about trusting your working knowledge and beliefs of how things work. Hell, you could even use this class as written to represent the kind of character that uses facts and bluster to wrongfoot their opponents. Many of the class feats in the playtest suggest this style of gameplay as a core strategy, such that focusing on debuffing looks to be the optimum way to go.
How often do you roll a crit-fail, tho?
At the very least, Make SW available at a lower level, say 2nd. That way it's on par with similar class feats (Expanded Spellstrike comes to mind). Thaumaturge currently feels like a duelist, in that its bread and butter is dealing with singular threats, but giving it more mileage tackling hordes would make it better to play, especially in encounters with a lot of enemies that don't share/have overt weaknesses.