For research job int increases job effectiveness by 3 points, research skill is 2 points and focus is 1 point. It is just additive. Once you get to a certain point you just won't notice the slight increase in efficiency.In the latest version, when I raise the research skill of my staff the skill is rising but without any effect. The research value stays the same. I guess, a nasty bug?
Your research department head's int, company efficency, and Ellie's optimizations are where any real benefit is shown. I also do not know how many employees you have in the research department nor how much you increase a character/measure the improvement.