There should always been the occasional adventure module where [Insert Specialist Type Here] is disadvantaged or even unnecessary on a temporary basis, just as there should be the occasional adventure where [Insert Specialist Type Here] is at a great advantage or virtually indispensable. But, on the balance, things should even out and the "default" should be that every given Specialist Type should have roughly equal "screen time" in any module.
If you were looking at a Star Trek module, based on what you know of the films and tv series, you'd expect a roughly equal split between challenges for the Science Officer or Doctor, Engineer, Security Chief, and Commanding Officer. So you'd try to have a mix of technology challenges, fight scenes, negotiation, and some sort of scientific anomaly. You might have a special "Mystery at Med-Base 7" module that is skewed to focus on the Doctor(s) role, but that should be a special thing.
]Shadowrun pretty much rests on four pillars: Magic, Matrix, Facetime, and Fighting. A balanced `run should have all four, in roughly equal amounts, and ideally it should have ways to use more than one of these means to accomplish the same ends.