Sacred Haven of Debauchery

Not on a large scale - no. But they weren't immune. As for controlling mages, I'll remind you about Uldred; he successfully concealed himself for a while, and then a good half of the circle became possessed.

Tevinter is the oldest state in this world. And so far, nothing more extreme than what happened in the "safe Circles for humans" has occurred there, such as: mass possession, the destruction of dozens of mages/Templars, and so on. What arguments could there be?

But, despite her obviously evil alignment, she wasn't subdued.

Not obvious. In any case, when she was in the Cagemasters, she complained about her difficult fate, but no more. I don't think the Templars knew about anything more.