I remember years ago when I was recruiting on a Java role to which one of the requirements included 3+ years of solid COBOL development experience in addition to 5+ years of C++. Being a contract developer myself I began to think to myself and wonder what kind of an environment is this to which they have three very different code bases?
The program manager at the time was not strong on the technical capabilities of the program so I suggested that I speak directly to the lead and inquire about these requirements. Within 10 minutes of a conversation with one of the tech leads on the project it became clear that they only utilized Java as their core base to which C++ and Cobal did not exist on any platform of any kind within the lab.
If you are struggling with roles to which you simply can't get qualified candidates, try working with the hiring managers to speak to the tech leads to obtain a real day-to-day description of what it is they actually do and the environment to which they work. This goes a long way when engaging candidates as they can get a good idea of how they might be a good fit for your role.