Tairn during the 'interrogation'

This post got me thinking.

https://www.reddit.com/r/fourthwing/comments/1p512i5/the_interrogation/

Why didn't Tairn go to any of professors' dragons, like Emmeterio's or Devera's or Kaori's? He must have known who is on 'the right side'.

Or even Nolon's dragon?

It was 5 long days of torture and pain. I bet he had a lot of time to think and find a solution. I suppose during that time he was anything but nice to other dragons yet he didn't think about other people who might had had an influence on Varrish? The only dragon that is stronger than him is Codagh and I suppose Melgren was not around to stop him. Was he?

The black are the cunning ones. Allegedly.

Any good explanation? Any other thoughts on how Tairn could have saved Violet (yes, I know Xaden rescuing Violet is one of the most romantic scenes ever but let put this 'minor' fact aside, :) if possible)?