The people who actually know this particular detail, about Talarius and Ruiden are basically going to be:
Talarius, Ruiden, probably Barabus and several of the other knights and knight rampant. Not sure how much the upstairs would know.
The Avatars know about the dagger because Sentir used it to kill Orcus and Sentir “discovered it” in fact, Sentir, Aodh and Lillith created Excrathadorus Mortis and as I’ve mentioned (somewhere) they used antimus to do it. It is in fact, the antimus in it (and a few other things) that is doing a lot of corruption in both Etterdam and Astlan.
In particular, Talarius dishonerable behavior (that he notes during the oath taking) was while under the dark influence of antimus.
We will discover much more of Ruiden’s origin and history in book 3.
Church corruption basically seeps in over the years slowly so you don’t notice it. Most of the problems are noticed upstairs because they are removed from every day activity. People are always at the best preying, and you don’t usually have a reason to distrust your worshippers and basically over hundreds/thousands of years everyone, including upstairs gets more used to the “little corruptions” so they become common place.
Only when the behavior is shoved in someone’s face, as what happened to Hilda does it become truly obvious. I still don’t think the extent is clear to anyone upstairs other then perhaps Sentir (who is working hand in hand with Evil) and now Hilda.
Remember, she has just been reporting. Think of this as a field support guy reporting stuff to a management team at a meeting. They really aren’t grasping the full picture and are frankly preoccupied by what they consider (wrongly) to be bigger fish.
Have B on the ground, should result in an eye opener.