To me, all the Colossus Titan did was open the door (I know the spoiler so it won't be mentioned, but I'm aware of how it could have been used). If the Banshee Titan could get in, it's over for everyone inside. One scream would demolish the entire city, or at least everything within the first wall. It's a bit more proactive is what I'm saying.

And yeah, Feces Titan is pretty gross. That's why he's so feared. 

I'm tempted to make a profile for Lea, Xia's mother, but I don't know if I'd use her enough to justify it.