It's darkly amusing that in this story with so much tragedy, there's some throwaway bonus tragedy in the first chapter. That guy in the first chapter who is asked about his younger sister? That's (almost certainly) meant to be Tiida Lanster, Teana's older brother, who has been KIA by the time StrikerS starts.
As for Fate being overworked (or overworking herself), it not much of a stretch; it was stated that Nanoha's injuries put her into quite the tailspin, and that she failed the mentioned Enforcer's exam twice over. Given the high-profile nature of Nanoha's case, and what we see from procedures in StrikerS and Vivid, it looks like the Bureau drastically overhauled their policies towards training, even if they obviously didn't decide to stop using what were effectively child soldiers.