Its amazing seeing these two routes side by side. Especially when you realize that with Meredith, this isn't just about finding a cabal of blood mages. This is a fishing expedition to find Orsino's involvement for the explicit purpose to justify performing the Right of Annulment on the Circle to Elthina. Especially considering that Orsino was right not to get personally involved to investigate. Because if he had, even if it was to stop the conspiracy, that would have been the death sentence of every mage in the Circle. And the reason why he isn't working with Meredith to investigate the mages is because not only is he afraid of getting those mages potentially killed or tranquiled if they were doing something innocent, he is also afraid of helping Meredith find an excuse to justify killing all the mages.
Many of my Hawke's would've joined the conspiracy, but they just fight you on sight even if you've been pro mage for the previous two acts. But they needed Meredith for the final boss. She should've been ousted in act 2 anyway.