Evolution has cracks?

One thing that makes me seriously doubt evolution is that in so many areas, very complex activities have to take place either simultaneously or in rapid succession and in a very defined order. Such as the dividing of a cell. Somewhere around 400 simultaneous protein related changes much happen simultaneously or the cell will not divide. Evolution requires small, gradual changes over eons of time. But so many processes that we observe necessitate sudden, simultaneous changes in order for a species to survive. Something to think about.