if there is no uninstaller, you can try reopening the .pkg file of the old driver, then going up to the File menu where it shows 'List Files' (or is it List Contents?). You could then manually remove everything. In reality, 99% of what you're interested in is in /Library/Printers/Epson/......... so you could just nuke that.
make sure to delete any Epson printer from the Printer Pref pane first lest you leave a zombie. It's also handy to do a backup beforehand