I also had problems with finding the 10 nobles. I think that's the only really downside of the quest. I found the first after 60 days the second after a hundred. Because I thought I only need 10 random nobles I stayed a long time at the same place, but of course I did not found any other leaders there. After day 300 I finally decided to finish this quest and could found the needed lords with the help of the encyclopedia. But yeah after 3 lords I had given up the main quest, because I just wanted to play and not to run over the map.
I see why they decided to the quest like this and I liked the story, but man this map is too huge. Also if you play on realistic speed and have 40 foot units you can't catch up with most of the lords even if they are in huge armies. And then you have to bribe your way into the keeps in the cities, which is reasonable, but doesn't help with the quest but also doesn't really matter since the lords do not to tend to stay more than 2 hours in a city for some reason.