Before we get the pitch forks out for Apple, its very, very possible (based on private email conversations I’ve had with some of the engineers mentioned in this post) that the problem is at least partially an Epson driver issue. Some of the drivers will use sRGB as the default profile which you can see in the ColorSync utility. This is not what “other” companies have recommended they do.
Drivers older than 6.5 don’t appear to exhibit this one issue, I can’t replicate it on an Epson 2880 or 3800 but CAN on an Epson 3880 using version 6.5.
A pitch fork for Apple for not documenting what’s going on with the OS is appropriate, I’ll give you that.
Lastly, if you do use Eric’s technique, its very important in the Print dialog of Photoshop to actually select the profile, not the same profile associated with the “RGB Working space” in the popup. IOW, if you assign Adobe RGB (1998) to the target, and your RGB working space in color settings is set to Adobe RGB (1998), DO NOT select “Working RGB” but instead specifically select the Adobe RGB (1998) profile from the popup menu.