I can sympathize with that. On the other hand, you're paying around 50k or more per year for your education, if there's something that you don't understand, you should probably ask questions.
Sometimes there are legitimate concerns about certain professors or unfair/plain bad teaching that needs to be addressed. If it's 10 people who fails a test out of 200, then it's likely that it's an issue with those 10 people. If there are 170 people who failed an exam, there are likely to be some concerns that needs to be addressed.
If you have legitimate concerns, letting the deans know by the end of the semester would probably be a bit late. But going to the deans should be an absolute last resort.
Of course there are always people who just hangs around and whines a lot without legitimate reason. Just avoid them, they'll likely fail.