I'm not sure how it is in Europe, but in the public higher education space here in the U.S. the unions are way to powerful.
An example of this imbalance:
All faculty and staff members for the California State University system are part of the same union. That means that the union has the collective bargaining power of all 50,000 employees. The union is very good at their job of protecting employees, and will always resist any disciplinary action by the administration, even if the employee is clearly in the wrong. This leads to a situation where administration will simply ignore extremely low-performing individuals because they would have to fight the union to do so.
Also, all CSU employees must pay the union dues, even if you are not part of the union, which is insane.
When unions are this big and this focused, their collective bargaining power, IMO, exceeds what is necessary to protect workers.
With the union you mentioned your a part of things seem to be better structured. Though it is large at around 140,000 members, they seem to be spread across many companies and I imagine that not every company is made up of 100% union employees. Also the fact that your union encompasses a wide variety of professions is definitely a big positive. That seems more like a fairer balance of power to me.