DBS is not a first-line treatment for depression, it is certainly not a cure as only about 60% of patients respond (probably less in reality, very few have had it and have been highly selected), and the remission rate is low. It is for people with treatment-resistant depression, those who have failed usually more than 3 pharmacotherapies, and typically psychotherapies too. It does not avail the need for pharmacotherapy, nor psychotherapy. It does not change the social circumstances that often contribute to depression, nor the characterology and early adversity that complicate the picture. I do not think it is going too far considering the treatment has only been used on a minority of patients and will likely remain only for the most seriously ill, refractory to other treatments. If it offers the possibility of relief of the torment of depression, without worsening the clinical picture as many treatments do, it should be available after other therapies have been tried. But it is not some miracle treatment.
Also Mayberg hasn't 'cured depression' -- she did not invent DBS, was not the first to try DBS in a patient, and is not a neurosurgeon and therefore does not implant deep brain stimulators. But DBS is one of the few functional neurosurgical treatments for mental disorders that are not worse than the illness they treat and if nothing else, it has changed the way we think about the neuroanatomy of emotion.