Her Majesty Queen Elsa, as well as Mr Pavus and Mr Iron Bull - those are the ones I have yet to see, here. With that said, I have yet to explore the whole place.
[...No, duh, Sebastian; it's been no time at all since the change. No one but you expects you to have covered the whole place already.]
As for when they were last seen, I cannot say. I could only account for when I last saw them - before the shift, on all three accounts.
[He... has not spent his time asking around for people, because that ranks woefully low on his list of priorities.]