On Varric and Cassandra:
Cassandra is just bad at interrogation; I am going to assume Leliana is even worst because she just lets Cassandra do it all the time. Varric was not properly informed of what was going on. Varric is very perceptive and he is rather 'person smart' therefore as soon as he ascertained that Cassandra was a romantic, he played that to his advantage and Cassandra was smitten by the story. Cassandra should not have gone straight to intimidation tactics because it put Varric on guard. Varric is what we might call a Neutral Good person. He prefers to do right by his close acquaintances, and he tries to stay out of grand politics etc. However, when push comes to shove he will do what is right for everyone. Cassandra could have confided in Varric, and as she said later, made him understand the importance of Hawke, but instead she had to stab a book and start a game that Varric plays much better than Cassandra. Cassandra is so bad at said game that at the time she did not even know that she was playing and got, as they say, played. She forced Varric to rely on his first instinct, one that most people share, to protect those closest to him. By the time she attacks Varric at Skyhold, she has no right to assault him, she is doing it out of anger and frustration with herself. Varric is not a 'lying snake', he cares about people a great deal, and he himself feels a lot of guilt over the spread of red lyrium even though that was not really his fault.