I'm GTA (Graduate Teaching Assistant) rep for my department - ie, a unionist, not something I ever expected. The GTA survey I did a month ago says: we are extremely overworked. We need to fix this by getting paid more - or by working less.
Problem is, the University decides how much to pay us per hour, and how many nominal "effort hours"to pay us per real hour of teaching. So we need to get in touch with other departmental GTAs and lobby them together. And we encourage Dave Sanders to pressure the university.