I don't think Vivienne was necessarily a bad character, but I cannot tolerate her for any length of time.
Her political motivations were too obvious, and I have zero patience for people who are clearly trying to use me. She obviously wants the restoration of the old order because she was poised to achieve power within that institution. She really has no other element to her character than being a sociopath.
Who wouldn't want a Margaret Thatcher expy with extreme sociopathic tendencies to preside over the resurrected remains of a failed institution? Every other mage might as well sleep with a Templar's sword at their throats, just so long as there's no hint that any of those rules apply to her.
Only basic, crude psychoanalysis of the character is required. She doesn't want power; she wants safety. Fear is everything, the core of her being. Her jealousy of Morrigan is probably the most obvious example of the profound insecurities that riddle her.
The strongest woman in the game is Fiona. There's a character who has been through hell and back-- literally. A minority faced with lethal discrimination who is villified for making a choice that was never a choice at all, but did so with grace and reason amidst systematic bloodshed. Fiona is the person I imagined my Warden from DA:O would be if ever I met them again.
Fiona has been dealt the hardest hand in Thedas. The scene where Alistair banishes her is probably the most poignant and agonizing of them all. And for a former Gray Warden who somehow lost the darkspawn taint to have to watch her son face the same destiny she was spared from by cruel chance?
That is a strong female character. Vivienne's only accomplishment is being an insufferable aristocrat who achieved minor political success. Get back to me when she's had a tenth of the tragedy Fiona has endured.