I have my friend keep a ret DPS offspec for fights when we don't need 2 healers.
He is ~ 476 iLvl and is struggling with putting out respectable DPS as ret, and he doesn't really know what to do and I haven't touched Ret since WoTLK.
Here are the logs of our raid last night where he was DPS the entire night.
Looks like he doesn't really use wings as much as he could and execution sentence. Inquisition uptime is pretty bad as well. May suggest to him to download clcret/info and give that a try if he is new to the spec.