Bug: Marshall Forwyn is not in Great Hall (Battle of Yenwood); Crowd is not outside great hall (A Return to Court) 

Repro notes: Appears to have been initially caused through beginning of Return to Court. At that time, the crowd was present but I had already clicked the entrance to Great Hall, causing the crowd to dissapear when I returned. 

As for Forwyn, I was able to talk to him about backing the army but did not yet have an ally for troops. Now that I have sufficiently rep with Knights and Dozens, Forwyn is missing. 

Consequence: Neither quest can be progressed as neither Forwyn nor the Crowd are available. 

If nothing helps you can unlock the Yenwood map with the console and travel there. Once you approach the battlefield the fight will occur (maybe without any scripted sequence) and after you won the quest will be completed. Even works if you didn't pick up the questline in the first place.