Ahmg! I'm going to have to try and get this on my current PT, I didn't even know it existed. I also need to work on figuring out how to get leliana Divine, I thought I had it last time but I ended up with Cassandra again ><
I always got my choice to become Divine. Is it really difficult? I only support the one I want - always. On the war table, but also in conversations. If I do not want Leliana, I tell her outright "You should not be Divine" and I do not ask Vivienne "What about Leliana?" etc. I really think it is key to make a choice early on (soft/hard Leliana, Herald or not, Divine) and stick to it in every situation.
Cassandra surprised me because I was sure I gained a lot of disapproval from her but she eventually became one of my Lav's best friends. Not complaining though.
I have yet to see the max disapproval/drunk Cassandra scene. Not sure if I want to. xD
I also got the max disapproval/trolling furniture scene from Vivienne. That made me laugh. 
Do it! Totally worth it. Because you can have both. First max out her disapproval and once you had that scene, be nice to her and she will end up with maximum approval. Of course, you should wait with all the quests that help raise approval (especially the apostate killing). But it is really easy to get her from foe to friend in one playthrough.
About Vivienne, I am not sure. I never got her to maximum disapproval, it seems, because I do not know her furniture scene. But I had done all I knew to raise her disapproval, so I think you have to give away all opportunities for approval changes to get her rating really low. Might not be enough left afterwards to raise it again.