This is a known issue with Epson printers...
I've seen this problem - dark prints with a calibrated LCD - with a client's Mac/Epson 3800 and could not resolve it. As it turns out there is bad bug in OS X. Bad enough that Adobe has posted a TechNote with a screwy work around:
Strange thing is the issue affects some users and not others. For instance my Mac/Epson 4800 prints dead on.