I think that people should be able to negotiate their salaries even if it leads to a large disparity in base salary. Without negotiations, companies risk losing talent.

However, I think the way raises are calculated needs to be revised. Currently raises are typically some percent of the salary and the range of percentages is fairly narrow (so the disparity remains constant). If instead raises were calculated with the goal of equalizing the salaries of like-performing employees the disparity would fade in a few years.

The problem with this, of course, is that lower paid employees get larger raises, which may seem unfair to the better paid employees. This can be solved by making salaries more transparent.

Although if salaries were more transparent then you probably wouldn't have as many problems in the first place.