You can't really farm approval with Vivienne either, unfortunately. Collecting her circle tomes only gets you 'slightly approves.' Bah.
If your Inquisitor's views don't really line up with hers like mine did, I guess you'd probably have a rough time getting her approval up. :S
I had Friends with Dorian, and it says he left for Tevinter. Confused me too, he said he'd stick around for a while. I'm guessing an option where he stays is romance-specific?
I guess. He leaves for Tevinter in two circustances. Either becauses he hates you and doesn't want to stay anymore or because he is inspired by your deeds and wants to change things the same way you did.
Vivienne can be rather easy to net approval without giving in to her Chantry extremism. I managed with many different options: Said the Ostwick enchanter was my mentor +5, saying the war is of no one benefit +20, told her we would need the circles again once it was all over +20, told Connor he deserved to die +5 (lol, I admit I aways resented him for Redcliffe), told Fiona she made an mistake by allying with Tevinter +5, saved the Haven people +5, made mage speech +20, finding all 3 books actually nets +20 from her, gave her the right heart +20, and drank from the well +20. Easily maxed her her approval with that.