Thanks for the replies;

When I wrote the original message, all three series were plotted on the
primary axis. I tried changing the series order again, but it didn't work -
and I can tell that it is because the lines are being covered by the markers.

(The series that I want on the bottom is just markers with no lines, and it
is a HUGE data set, really more of an array of performance data points, and
it blocks out huge portions of the chart. That's why this issue was so
annoying, all the markers were almost completely blocking out the lines of
the other two series).

I tried plotting the two lined series on the secondary axis and that worked
perfect! Good enough at least for this chart.

Hopefully future Excel version will improve the layer options as you have
noted.

Thanks for the responses!