It is now 2016 and I have a Macbook Pro (purchased 2014) and Macbook Air (purchased 2013) and had the same problem. My operating system is OS X El Capitan (10.11.3)
If you keep trying things you finally stumble on something that works. Here is what finally worked for me.
I have an Epson WorkForce (WF-3620) which is an all-in-one device. Driver updates keep coming in from the App Store. One good habit is to delete your current printer (in System Preferences/Printers and Scanners) before you download the update. After the update for the drivers has finished, add your printer and faxes to your list of printer choices (in System Preferences/Printers andScanners). Because you have deleted the old devices, you have essentially installed a new printer, although it is not a clean install. So, you MAY (or may not) have to re-enter your wifi password and re-set your fax options. Do some trials and find out for yourself. I find that I usually have to reenter the wifi password on my printing device with every driver update.
Now, find something that you want to fax. Select Print and the Print Dialog box opens up, and then select your fax machine. You will find that the Fax option is greyed out at the bottom of the dialog box. That's OK. There's a dropdown box under the settings for paper orientation. The default setting on that dropdown box is Notes. But drop down and and look at the other choices. You will find one called "Fax Settings." Select it.
Then, go to the device list (also a dropdown box) at the top of the Printer Dialog box. Change your device from Epson Fax to Epson Printer. Now, at the bottom of the dialog box, the option FAX will appear, and it will be viable.
