I've been thinking about the character situation and I think a few things happened that were unexpected.
1) There were no waves for corral releases, so the balloon ladies started sooner than they would at WDW and people had less of a buffer for photo lines. I think this may have surprised some people who are used to running at WDW and who know they can have more than a 16 min mile if they start early enough.
2) Maybe DL didn't anticipate the demand for character photos? I know characters here tend to just wander a lot in the parks and do quick little pop ups, vs WDW where people will stand in line because this may be their only trip and they want that character photo.
3) Related: they seemed surprised/annoyed when people were trying to take photos with non-line characters. I ran by Chip and Dale in the half and people were trying to at least stop for selfies with them and were shooed along.
4) I heard of at least one, maybe two incidences during the 10k where it seems like cast members or race staff lied (misrepresented? were misinformed?) about where the balloon ladies were in an attempt to keep people moving. This is not first hand knowledge, just my interpretation of what I heard, but if it's true using the balloon ladies as boogie men is definitely not the image those ladies want to project, and isn't a cool thing to do to back of the packers.
5) as
@fatmanatee said, character lines are crowd eaters. Maybe not having them contributed to the course crowding?
I don't know. I'm new to all of this, so these are just guesses/thoughts. I hope things will be better for the Halloween races, now that they've seen what some of the issues are. Pre and post-race character photo ops would help, I think, along with more (and better managed) character stops in the parks.