I have a G5 and an Epson C86 printer. Epson's printer drivers have not worked for either Panther or Tiger. In both cases Gimp print drivers worked well. The drivers need to be selected in the print setup utility.
You didn't say if you've actually got to the Epson drivers by first selecting Epson USB? In Tiger, after clicking ADD, don't accept the printer, but instead click on More Printers and then select Epson USB. Now you can select the printer and it will be using the Epson driver.