Yes, the downsides of at-large reps would surely be that if no one rep is responsible for particular local issue(s), it’s possible that none would take it up and that would leave some constituencies unrepresented. My thought about that is that when district maps are drawn to purposely divide particular constituencies (I mean, look at all those pack-and-crack maps that split minority groups into districts that mostly elect people that don’t represent them), an at-large system might allow those constituencies to unify around particular at-large reps?
I don’t know, I’m spit-balling here. But thank you for taking up the question constructively!