Firstly, I want to say that I liked Greymoor's questline. I particularly loved the side quests (Narsis Dren's quest had me laughing the whole way through). However, Greymoor's main questline is far from my favourite. I don't think it was bad, but there were some very minor, perhaps pedantic things, that I personally felt took away from the story. While I realise it its too late to change the story, I write this in the hope that there will be more consideration for future expansions.
The character I have feedback for is Princess Svana. I don't have any criticism of her overall personality or anything. I actually find her quite interesting, a rebellious princess who doesn't care for her title, who has to end up stepping up to save her people.
However, there's one story decision that really confused me. And that was the decision to send her to Blackreach to investigate the camp. This was incredibly odd. Blackreach is described constantly in the questline as being a very dangerous place. Svana, after all, is the Princess and future of Solitude. On top of that, out of the three characters you have to help, Lyris and Fennorian, she has explored it the least. I feel that the more sensible move would be to send Lyris to Blackreach and have Svana up in Western Skyrim, since she grew up there and would know the land far better. Or at the very least, have one of the characters question the decision.
This leads me to my second bit of feedback about Svana, this one I think is fixable. Currently, throughout the entirety of the questline, Princess Svana wears the same clothes. That to me was also strange. Svana clearly knows how to fight and also has the gold, surely she would change into some armour before she went out fighting. Visually, I think in future expansions, it would be great to have characters be more dynamic in their choice of attire. It's little details that really make Elder Scrolls games great in my opinion, but I feel that some of those details were missing here.
Again, these points are very pedantic and I'm not sure if anyone else noticed or took issue with it. They're not game breaking either. But I think it's just those tiny details that really count. Other than that, I am enjoying the rest of Greymoor, and I adore the Antiquities system! Can't wait to see more of that.