1) Remove inquistion's GCD. This could be done with a glyph similar to the deep freeze glyph for mages. As it stands right now there aren't any glyphs that stand out for a ret in most pvp situations.
2) Reduce the cooldown of Avenging Wrath. Reducing the cooldown of this ability to help it better allign with holy avenger would work wonders for ret pvp. It could be changed to 10% - 15% damage increase to help compensate.
3) Divine Purpose baseline. I know you guys see this a lot and always have the same answer. We maybe don't like the RNG aspect of this skill but it's honestly the only way to keep our sustained damage up without removing it from the game completely and replacing it with something different.
4) Another thing that ret definitely lacks is cc. With the increased amount of instant cc added to this game, removing repentance from rets really hurt. I know you gave blinding light in return but against good players this skill is incredibly hard to use effectively. Especially when compared to other similar cc's of other classes.
These are just a few suggestions that I've though of or seen in other threads that I think would steer ret in the right direction, as far as pvp balance goes. I wrote all of this on my phone and I wish that you add any thoughts or suggestions that you have came up with.