The provost’s office will want evidence, which means (a) more than one person complaining, (b) people have to be willing to give their names and show their test scores, and© be prepared for retribution on the part of the strict grader. The last one© is somewhat of a risk. If you think it’s worth the risk, then go to the provost, because it sounds like you have a legitimate complaint. But you will be more successful if you go as a group and can make a general case.