But no circle mages. Personally, I found it fascinating to hear the perspective on the mage rebellion from a mage who did not support it. That's a perspective that you wouldn't have gotten anywhere else. Even Wynne had her grievances with the circle. And the banter concerning circle teaching methods and the limitations thereof with Solas were definitely worth her being a party member. Magical theory is one of the most interesting parts of the lore.
You do get that if you talk to the mages in Redcliffe, and from Minaeve, for example. I really don't see anything unique that Vivienne brings.
Well I did mention Solas.
But my point stands. Most of the party members don't undergo any huge epiphanies during their time with the Inquisition. If you're talking character arcs, then Viv does soften somewhat towards an Inquisitor who gets her to high enough approval. And for Vivienne, who has worked very hard to excise even the suggestion of weakness, this is rather heartwarming. But my favourite his her banter with Cole where he reveals that she does care about him after all, but that she was afraid to commit herself to caring about him because she didn't wish to be hurt. There's also the suggestion that she's a tad jealous of the Inquisitor and their love interest. The Inquisitor has the luxury of choosing their partner for love rather than political advancement, something that Vivienne has never had. However, she also evidently cares very deeply for Duke Bastien, and his death is the only time you see behind the mask. Other than Solas, Vivienne is the most guarded character in the Inquisition.
I'll have to listen to her banter with Cole again, because I didn't get that. But really, there was little chance I was going to get anywhere with Vivienne, because I'll never have her approval anywhere close to where the relationship is even cordial. She can redecorate my furniture whenever she likes, though, if it helps ease her aggressions. lol