I will say this about Vivienne specifically. I Love the character, specifically because she's such a terrible person. Not in the simple sense like Corypheus is.
She's selfish, ambitious, power hungry, attention seeking hypocrite.
"Oh yes, look at all those terrible mages who cry about their poor treatment, why they can't even look past the wall of Templars threatening to kill, torture, and/or rape them to see the bigger picture. Which I can see clearly from my suite in the Duke's Massive Mansion." She didn't live under nearly the same conditions as most mages and still blames them for everything that went wrong. ( She all too quickly blames Cole for antagonizing the mages with his early murders but completely refuses to even acknowledge the pain and suffering that attracted Cole there in the first place. ) She clearly doesn't much care about making things better, only about removing the chaos that threatens her precious court standing.
But she's also extremely smart, capable, determined and extremely skilled at dealing with anything that's put in front of her. She will always have good advice for you which she provides in earnest for the simple reason that you asked. She accepts nothing less then the best possible solution, so you always know what you're getting from her even if you don't agree. She handles the people around her with such skill and finesse, and she never allows anything to so much as fluster her. Even Empress Celene couldn't match her in that regard.
So I have great respect for Vivienne, and would always welcome her skill and counsel. However I still don't like her and would never be friends with her.
But then that's why I think she's such an awesome character. 