Before the game came out, I thought she'd be a sort of Wynne, only Orlesian and thus slightly snobby and very stylish, experience restricted by her Circle training, but open to new ideas, like Dorian was restricted by Tevinter ideals but open to new things. -- OH, and like many others, I thought she'd be a romance option for male characters.
It quickly became apparent that she would see little but the inside of Haven's chantry/Skyhold as she's intolerant of my favorite companion (Cole), because I couldn't take her anywhere without hearing her sniping at him. Creature this, demon that, blahblahblah. I had Solas and Dorian to be my mages anyway. While I like the idea of her character being mage nobility, having to leave her at home all the time made her boring to me.
Heh, when I found out Vivienne was a possible Divine, I did everything I could to keep that from happening--wiki spoilers, everything.
However, I do like Indira Varma, Vivienne's voice actress, who I think performed wonderfully.