Complex cases are applications with multiple dependents, extensive travel history, multiple residences across different countries, complications can include inability to get certain documents like work references, and so on.
I remember a lady here who could not get any work references from employers, and she had to submit alternate documentation. But she got PPR early on.
@faridbaig, I understand the frustration completely. You can't help but compare at times.
But you're on the last stretch, all i can really tell you is to have patience. Calling them and sending e-mails, i really don't think it does anything.
Keep checking for GUs.