Nope.
You also forget that one of her low approval divine endings has Cass use the seekers to violently crush her opposition, so she isn't opposed to violence to stop opposition.
As superdarkone said no.
She calling Vivienne a tyrant is very difficult to know why because of that and beyond Vivienne using violence to quell the revolts there is nothing else indicating why she would be a tyrant.
So, taking all that into account... I don't doubt the honesty of Cass' opinion. But her being honest doesn't make her correct. So I'm gonna respectfully disagree with her. (Please no one interpret this as dislike of Cassandra, cus she's pretty much my fave in the DA series. I just love her for her flaws/quirks, too. lol)
I don't necessarily think Viv should be Divine, personally. I think a Divine, like a Pope, should have a strong faith life. Faith should drive their agenda, not the other way around. Unfortunately for me, the only one I feel fits that qualification is Cass and I really want her to rebuild the Seekers. lol
I do find it amusing and rather gratifying that Viv would threaten to declare a March on Par Vollen on the Inquisitor's behalf, though. True friends help you bury the bodies, etc.