I believe they mentioned really briefly in the first episode that healing magic is quite rare in this world. Also, that there are two other healing mages in the city, but they are not usually living with the rest of the Rescue Squad (we will meet them in the future). If I remember correctly, we do get to see how the gang of non-healers fit into and help the squad, so I won’t go into details here, but they are more or less meant to be support to the actual healers.