Thanks for your respective comments and suggestions. I'm starting to think that the issue I'm dealing with here is either gloss differential or gloss artifact, as defined here:http://www.incits.org/tc_home/w11htm/2001d...differential%22
"Gloss artifacts include such items as streaks and banding that are one-dimensional in nature, and patches that are a form of two-dimensional, possibly sparse, mottle. Gloss bands, streaks and mottle are most easily evaluated in flat fields of uniform density."
I see mottled or "water-stain" artefacts in EEM/4800/MK most easily under strong incident light at a 45 degree angle. Previously I had said that this effect was restricted to the darkest of dark tones, but now looking more carefully at my entire test chart (see attachment in previous post), I can see significant reflective mottling in several of the Gretag Macbeth Color Chart patches (e.g. moderate red, purple, red, neutral 3.5), and less significant but still clearly visible mottling in several other patches-- again, when the print is held at an angle.
These facts lead me to believe that my original gripe about EEM is an ink-density-dependent effect that isn't going to go away unless ink density is measureably reduced. This brings us to the points & suggestions you each made (and thanks for those, BTW):
Mark>When you dial down the ink, you may also sacrifice some dynamic range, but that could be the lesser of two evils in some cases.
Don>as a simple test why not try the printing the problem image using Ethan's profile and WC/RW media setting? This isn't ideal (profile should be made from same media setting) but I find that it works within reason, and might tell you if it's worth getting another profile made.
For my experiment, I printed my composite test image via the Dry Creek EEM profile, on EEM paper, but with the "singleweight matte" media setting in the Epson driver, rather than the EEM setting. I found much less severe (but not eliminated) gloss artefacts, as well as significant shifts in the lighter Gretag Macbeth hues.
Mark>why not try another profile for the troubled images?
My experience has been that really good custom profiles produce significantly better prints than non-custom profiles. Having read "Real World Color Management", I'm not inclined to get into profile tweaking / editing. It's unclear to me at this point whether it would be preferable to get a new custom EEM paper profile for the EEM media setting, or for another setting, e.g. Singleweight Matte. There are risks of dissatisfaction and wasted money either way.
OTOH, gloss mottling is evident at 45 degrees in the Hahne. Torchon 285 test image print as well, so there are a number of variables to sort out... ay yi yi! My next step well may be to get a can of Premier Art spray and see if that can even out the surface finish.
p.s. Don, FWIW, I don't see immediately why WC/RW would lay down less ink than EEM. It makes much more sense to me that the first set of paper types listed in the Epson driver would be ordered by increasing ink density: Photo Quality Ink Jet paper, Singleweight Matte, Enhanced Matte, Archival Matte, Watercolor.