I respect Vivienne - she beat the odds and worked her a** off to get what she wanted, she's smart and competent, not to mention politically savvy. You gotta give her that, at least. And, when she wants to, she can be the most earnest and genuinely friendly person.
But at the same time she can be a cruel, opportunistic and elitist a**hole who is all too happy to use manipulation, half-truths and outright lies to get what she wants. She's also one of the "I got mine, so **** you" people who are all too happy to kick the ladder down after they've reached the top to stay at the top. The Game taught her well.
All in all, she's a superbly written character.
Personally, she's one of those characters I love to hate, although there are also moments when I sympathise with her (her personal quest, for example). But there are just way, way too many moments when she just makes me want to punch her - like, she keeps talking about the civilians and the mundane people's right to safety against magic, but lo and behold if you raise the "people" flag the highest during CotJ... "Vivienne slightly disapproves". Why am I not surprised.
OT:
We're basing things off of Mana Clash???
An ability EVERYONE (including Bioware itself) said should either have not been made or significantly weakened (it was a better anti-mage weapon than the ability of templars who actually suppress the connection to magic itself).
LOL, Mana Clash is so ridiculously OP. I think the first time I used it I got the Hard Hitter -troply... and I was really low-level and trying to get past the bounty hunters outside Orzammar. After that it became my standard "I Win" button against all the enemy mages.