We know for previous WoBs that Truthwatchers are worried about knowledge and helping people with it (https://wob.coppermind.net/events/176/#e8500). In the test you recently released, the new info about them says that they are worried about the use of the knowledge and the leaders trying to deceive the people they lead. So, I think they have some things in common with Windrunners and Edgedancers, because the three Orders are more worried about the common people than about the elite. Protecting those who can not protect themselves, remembering those who had been forgotten; both of this Second Ideals refers to the common people, that people that the leaders don't really care about.
Considering all of this, and following the example of the Second Ideal of Windrunners and Edgedancers, which are the most worried about the common people with no epic powers, I wrote a theoric PURE (without corrupted sprens like Glysn) Second Ideal for Truthwatchers:
"I will seek truth, to prevent others from being deceived."
I know you are RAFO'ing this, but I would only like to know if my approach of the Truthwatchers Order is correct.
[That] is, I'm afraid, a RAFO as I don't want to talk too much about the oaths of given orders until I write books about those orders, as it would constrain the story a little too much. Your theorizing is sound, however.