IELTS is not required to qualify for a German work visa.
The English language requirements are dependent on the type of job you are applying for. If the job is for a position that involves traveling around the world, then a certain level of English proficiency is required. In such cases, it would be no harm to get an IELTS certification which is a validation of your English proficiency.
The right educational qualification, work experience, and a basic knowledge of German will improve your prospects of finding a job here.