The short answer is YES. The therapy is normally used to reduce the disease-associated pathological manifestations. Therefore, it is important to know the causative agent(s) that is associated with a particular autoimmune disease to target the agent for biological therapy.
Definitelly, most of the patients with ADs have benefits of biologic therapy. However, there are cases that are resistant to this therapy, and you have to "switch" or "cycle" biologics untill you get the proper answer.
Yes, biologic therapy has been found effective against several autoimmune diseases. For eg. Tocilizumab- which is a monoclonal antibody, used for the treatment of Rheumatoid Arthritis, Systemic Juvenile Idiopathic Arthritis, and Castleman's disease.