I'm having problems with that questline as well. I'm stuck on the "Compelling Tribute" quest! Legate doesn't have the dialog to trigger that quest and visit Anuriel. I have reloaded saves numerous times, but the only dialog I get is "why do you fight for the Imperials".
Well, here is a weird one...I finally got the "reporting for duty" dialog, and instead of sending me to the next quest, which should have been "Compelling Tribute", she skipped that one and the next, "The Battle For Fort Greenwall" and sent me to "Rescue from Fort kastav". Maybe I'll get to play those quests in my next character...

I think what caused this was that while trying to get the "reporting for duty" dialog, I decided to pay a little visit to Fort greenwall, I was gonna leave before hostilities broke out, (I promise), but one of the Stormcloacks sent an arrow my way, and then thay all rushed me...I called in my dragon buddy, and in less thsn 30 seconds, there was toasted Stormcloacks laying everywhere.

I reloaded an earlier save, returned to the boss and got the correct dialog, but it skipped over two quests. They aren't in the completed quests either. Was a lot of fun though...
