Three things come to mind. First, people who teach languages for business and professional use have a competence level system (which I do not know) that is fairly specific. You might be able to find a lot about it on the Web. So far as I know, there's no "rule" that says one must apply it to one's work.

Second, most counseling, mental health evaluations, etc., are so heavily dependent on idiom, nuance, cultural nuances, etc., that working in a language other than one in which one is very familiar with both the words and the person's background seems quite dicey at times. I encounter this in the opposite way: teaching and working with trainees and practitioners from other countries/cultures. Virtually all of them are extremely bright and well-educated (they have to be in order to get into the US and a US-approved training program after completing medical school in a different country/culture), but inaddition to the "science" of medicine and psychiatry, we must expect them to be able to understand the psychosocial aspects of even the most biologically-based care. Some of my trainees have done extremely well for themselves and their patients; others have not.

Third, about translators: There are LOTS of problems with using translators in detailed evaluations and treatment. It's too big a topic to get into here, and I'm not all that experienced with it, but suffice to say that simply knowing the language well is not sufficient for choosing a translator in clinical work. In emergencies, one has to use whatever is at hand, of course, but there are many unfortunate stories about situations using relatives, telephone translation services, even a custodian from another country.