I wouldn't say that Ul'dah is the place to be anymore. Since 1.18, a lot of the population is spread out more. I've seen a ton more people in Limsa than what used to be. I even found Ul'dah to be pretty empty :S I would still say to try using the seek invite in the party search or sit near the dungeon entrance. Maybe it's just your server, but on Besaid there are usually a couple dozen people there.