Don't ask for rbg rating as proof period. The amount of win trading and rating inflation this season is too high. I have seen rets with over 2200 in rbgs this season, I also know for a fact they used the win trade exploit to do so.
On that note though, holy paladins were told to go ret for arena in cata. Resto shaman and disc priests were better in pretty much all viable comps.In Cata every Ret heard: just go Holy, Ret brings nothing to RBG and only ultra hardcore players can do something with this spec. Go Holy.