Sadly Dorian bugged out on me so I never got to really know him
I did "personally" care greatly for Cassandra, yet I never felt a sense of closeness pop up between her and my inquisitor. In comparison, Hawke and Aveline were like brother and sister. That's probably just a personal response though.
Ironically enough, I felt the friendship with Cass build up over time when I chose to ask the mages for help. So, she did end up feeling like a friend to my Quizzy. On my second playthrough, I went with the Templars, and Cass' approval skyrocketed, so there was no build-up. All of a sudden I get her personal quest. But, because I got so attached to her during my first run, I am still very fond of her 
"I would drown us in blood to keep you safe" What's not to love? 
That is one awesome line, I'll give him that
It will be probably the only one I am keeping for my fanfic, though it will be said in a different context 
To be honest, even Viv can seem like good friend material depending on the IQ. For some reason she flipping loved my dual-dagger rogue. I have no idea why since I thought I treated her the same as others. Her dialogue was completely different. She was all like "You look terrible, my dear...let me have a look at you. I need to take you out for a spa day." and "How can I help you, my darling?" With my other IQ's she would be downright cold and nasty to.
Oh, Viv became very friendly with both my mage and rogue Quizzy - darling this and that, seamstresses, decorations, spas... I love the VA (she was awesome in Rome), but there is a certain aloofness to Viv's character that makes her feel more like a mentor and advisor rather than a peer and a friend. On the other hand, Dorian turned out to be a sweetheart, once my Quizzy got to know him - the way he expressed how much he valued the friendship made my insides go all mushy
And Cassandra impressed me with how she changed her view of my character over time, how she grew to respect Trevelyan. But for this to work, her approval must grow gradually. Otherwise it can seem like a sudden 180