What can we do after entire class failed/barely passed? Completed an essay worth 30% of our grade over the Xmas period and were given incredibly strict instructions (no sources other than the 10 pages given, 1200 word count, marked 50% language and grammar [german] and 50% content). Got my grade back and got 32% which is my first ever fail of my life. Was slightly discouraged until I learned that nearly the entire group failed or got 42/43/44?

The essay was also given to another branch of the course (politics and computer science) and they all passed with quite high marks (60% upwards). I completed a similar essay for another subject and got 57% and another where I got 65%.

We all feel that we have been unfairly marked, but despite being in the best university in our country, we are too scared to ask anyone in the department. All the colleagues stick together and would definitely take the side of the markers and imply we're all stupid.

My essay wasn't amazing but I definitely don't believe I deserved to fail and others don't either...

So my question is: is there anything we can do to change this?
Talk to your student's union.

They should know whether or not there can be anything done and if yes, what. They should also know if a situation where everyone fails is common (in some universities there are some courses, mostly freshman-courses, where it's common that 90% of students fail) in your country/university.

But prepare yourself for the possibility that nothing happens. In my experience, the situation that two groups/individuals are graded obviously differently, is very common in the university level. In my university, for example, there is no quality control of the courses whatsoever - a course is taught well/ is fair if and only if the instructor wants to teach it well and wants to be fair (and is capable of teaching well and being fair). Fortunately, many academics are "good people" wanting to be a good teacher (without being rewarded) but some don't care at all (which can also makes sense, since they need to focus on publications to survive).

But what can you learn from this situation? You can take some steps to prepare.

1) It's always a good idea to find out what the exact rules are for taking courses in your university. Can you switch the order of the courses? Can you choose instructors? Can you do exams with instructors who held the course some years ago (but you took the course with someone else)?

2) If you can choose instructors, then try to find out something on them. Who teaches well? Who is motivated? Who treats students fair? Who helds female and male students to the same standards? (Unfortunately, not everyone.) What about foreign students? Who grades fairly? To find things like that out, ask your student's union, socialize with other students, read things in facebook groups, maybe become active yourself as a student's representative.. These things will help you a lot.
If lists are avaiable on who will teach courses in the future, try to adjust your courses (if possible) such that you get the good instructors. Remember that, of course, your goal should not be to just get the easy-grading instructors, but the ones where you learn much. (But nobody is helped if you learn much but fail the exam because the instructor belongs into the (unfortunately, non-empty) category of people who let everyone but women with very revailing clothes fail).

However, be advised, that unlike popular belief, there are many harsh graders where you don't learn much and their are many easy graders where you learn a lot.