I'd be careful about inferring too much from raw data send to a CMYK printer through an RGB driver. In theory of course, the driver, in a color managed scenario would make any necessary adjustments to what you're seeing to hit the required hues.
I'm not disputing that you have a color issue. One thing I ran into here was inconsistent color output, literally from print to print. Specifically a magenta cast or alternately dark, slightly washed out colors. After much troubleshooting it seems my problem is computer specific. I have run the same test prints from a second computer that all come out as expected, with saturated reds, deep blues, etc. I'm going to reinstall the driver on the problem computer. Do you have access to another machine with the driver loaded?
I will say that for RGB profiling I'm getting better results right now from PrintFix Pro. I know, this defeats the whole purpose of having a built-in spectro. Still have more testing to do to make a definitive statement. Have you tried creating a profile with something other than the on-board software?
Looking at the test chart, especially patch E20, this is what I would be happy to get as base Red, however the best my machine can do at the moment for an uncalibated chart would be E13.
The same would apply for A20 and F20 with the best my z3100 getting being around A14 and F17. If I create an uncalibrated chart with CMYK ramps and RGB ramps the CMYK prints correctly while the 100% RGB patches print Orange, purple and light bright green. This already says to me there is a problem with the colour mixing.
I have attached a sample of how the two printers will print the same chart. On the left is the Z3100 on super heavy weight matte and on the right, the epson 4000 on enhanced matte.