I had once been on a tour of a prospective centre when I heard a staff member say to a 3 yr old ' if you don't sit at the table, i'll cut your legs off'! This is so not acceptable. How would that staff member manage worse behaviours?
I understand your concern about being a 'rough' group. Sometimes different combinations of children can have that effect. Staff should be aware of this and adjust the program accordingly to redirect the 'pack mentality' and use appropriate behaviour management.
If you can, I would encourage you to take advantage of the 'open door policy' that most centres have. You can find out just what really happens during your childs day by picking them up at differnt times of the day.
You were right to go to the director, how many other parents may have issues with the same person and not done anything about it??
You wouldn't put up with a dodgy mechanic working on your car - why should we put up with anything less than perfect from the people that care for our kids?