That's weird because I was sure killing the dragon at the Whiterun watchtower is what makes the dragons come out. I kind of delayed the quest in which you first see Aulduin awakening a dragon with Delphine and I'm pretty sure I killed quite few dragons before doing that. As a matter of fact I know I killed a few dragons before that quest. So I think you should have triggered the dragons by now.
Yeah, I thought so too, but I NEVER had any dragon encounters ever since that jurgen windcaller quest.
Just did the quest with Delphine, I hope I will get to see a dragon soon, if not I will continue to pursue the MQ.