If they're giving a speech about their motivational backstory at any point, they're probably doing it wrong to begin with. It's not an issue of spreading it out more. If a character struggles to seem real without me knowing about their abusive father, they'll probably struggle with it after, only now I'll hate them for making me hear about their father. I didn't really need to know that Jacob hates red tape. I got that from Garrus. And that was the point of the Spectres. It's time to move on. I can believe it in new characters without having it being explicitly stated. I can make inferences based on reactions to events. Aveline's a pretty good example of the writing being done a lot better.
If they're not present to react to an event, I probably don't care about them enough for them to need to develop for me.
All you're doing is describing ME2. I think we all played it. We know what they did. But the narratives of a game should tie together. They should make a bow.