What to do with teachers who think their subject is "extra special" and gives students too heavy a load?
This is just what you should be expecting from your postgraduate degree. Each module is special. It should push you further than any undergraduate module would.

You are also now assumed to be a grown-up, and to learn how to manage your own workload, and to balance competing demands on your time and energy. Part of what a Masters or Doctorate course does, is to teach you research skills, and project management. These are (at least, in the courses I've been involved with), an important part of the process.

If you are having trouble balancing your workload, talk to your personal tutor, the graduate tutor or whoever else it is who's been assigned to you by the department to manage these cross-module issues.