I think what you are looking for is to see your individual workers on the chart itself.  each one of the boxes after the one that has "all" in it can be used to put individual workers or groups of workers.  I don't know how your workers are named but I can use a couple of mine to give you exampls:

If you take a couple of my workers, clg3.29s9, clg3.30s9, clg3.31a821 you could fill in boxes with .29s9 and .30s9 and .31a821 and click Update, all three will appear on the chart along with the "all" line.  Just be sure to start with "." or "_" depending on which way you named your miners.

You can also use wildcards...if I did .3* in one of the boxes it would group both the 30s9 and 31a821 into one graph line.  I could also do .29*, .30*, and .31* to list them as separate lines on the graph as well.

EDIT: When you put in mutiple miners of similar hash rate they will overlap each other but you can uncheck a couple of boxes without changing your configurations to look at one or another.  You can uncheck all boxes and selectively check one at a time to get a clearer picture.

EDIT2:  Thanks VRobb!  I kept getting sidetracked before I hit post so it took me longer