Have you checked the wiki page? If you remember your choices you should be able to do some maths to figure out who's winning...
http://dragonage.wik...Divine_election
As for the missions not turning up, have you completed WEaWH yet?
I have. Unfortunately, I am one of those who makes friends with everyone so it could be any of the three.
Except Sera. I recruited her long enough to get the achievement then went back to an earlier save and didn't re-recruit her. There's just something about her initial impression that I can't get around and she doesn't seem the type of person I would want as a representative of the inquisition. Even folks in the Haven tavern had nothing good to say about the ruffian elf by the tables.
Your question about the Winter Palace is interesting though. Let me tell you about what happened there.
I had been romancing Cassandra. I hadn't gotten to the part where we consummate our affections, but I had literally talked her out. Up until that point, I had flirted with her on every occasion that arose in our conversations and had flirted with NO ONE ELSE. (I like to pace myself or I run out of main quests and companion quests and end up with nothing but a ton of side quests. Besides, I like being a level or two above the main quests. Fights end a lot sooner that way).
To the Winter Palace I took Cassandra, Dorian and Vivienne.
Now when I romanced Dorian and Cullen (twice each) the same way, at the end of the Ball they came out to talk with my Inquisitor and we danced.
This time however, it was Josephine who came out to me on the balcony. I was shocked. Where was Cassandra? I had done my duty as a potential boyfriend and had asked her for a dance earlier on, which she shot down, and I had noticed that I had no options to ask any other companion to dance. I thought this meant I had sealed the deal. I guess not. I did ask Josephine for a dance though. The way I looked at it, I had asked my lady love for a dance, she turned me down and now here was another friend asking if I was alright after such a long and exhausting night. I wasn't going to let my Inquisitor go through that whole thing without having danced with anyone but Florianne, and while Josephine wasn't the partner of my choice, it was considerate of her to care... so we danced.
What I found amusing was that once I was back in Skyhold, and sought out Cassandra, instead of having a conversation about the Winter Palace, I was treated to her "courting" scene. It was almost as if she thought, "Hey... he was dancing with Josephine, maybe I should quit playing hard to get."
So, to answer your question, not only have I done that quest, but I have even turned Calpernia against Corypheus and drank from the well.
As far as my choice in the Winter Palace, I always bring the Empress and Briala together. I also supported the Templars and didn't banish the Grey Wardens. There's just something about having all those extra swords for the Inquisition that I find hard to turn down, and even though they can be influenced, we need Grey Wardens for the next Blight.
@Gervaise... Looks like it will likely be Vivienne then. Well... shite.