Going back to your own "hijacking" of the thread, Greg - I also never got really pure mono prints until I upgraded my printer from an Epson R1900 to an R3000. With the former, no matter how carefully I tried to cross-calibrate my monitors with the printer using ColorMunki or, alternatively, no matter how assiduously I used the correct manufacturer's profiles for papers and ink, I could not consistently get mono prints that were entirely free of any slight magenta or green cast. I don't think this had anything to do with Lightroom.
The R3000 does not use the colour inks to produce mono prints, having, instead, three "shades" of black ink. Now I get no colour casts at all. Perversely, I get the best results when using the bog-standard Epson "Advanced B&W" profile, rather than fannying about with custom profiles, and telling Lightroom to allow the printer to manage the printing.