In arena they’re alright. Solid 5/10. Not meta, but not worthless. Fairly gear dependent. But by the time S3 rolls around and you get that Vengeance Sword and a real nice spell power on-use trinket you can absolutely 100-0 someone in a hammer of justice with stacks and wings.
Obviously Ret/Rshaman is the predominate Ret 2vs2 team but don’t sleep on Ret/Spriest, Ret Disc Priest and Ret/Dreamstate Druid.
I played Ret/Restokin on Endless a while back and it was extremely powerful. The Ret can dispel magic and keep roots / snares off of himself and I can dispel curses and poisons. The Ret could put Sacrifice on me during hardswaps or all-out BoP me if I’m caught with my pants down. The CC was highly effective too, with Hammer of Justice and Repentance both being instant cast and off DR with Cyclone. We could easily force trinkets early and then Repentance --> 2x Cyclone with wings, one-use trinkets and me pounding 1200 damage wraths with Moonfire and Insect swarm ticking. We could do about 15-20k damage together in the ~10-15sec CC chain. Very little survived. And, if we had to pull back, it’s a great comp defensively. We can pillar and cleanse ourselves all day. Ret’s biggest downfall was mana efficiency. And Mage/Disc comps farmed us. Other than that we were quite competitive.
In BG anything is viable. It doesn’t matter. You’re going to feel very immobile compared to a lot of classes and your damage is going to feel low outside of your burst windows, but if you use your utility right you’re a great asset to the team. Embrace the hybrid nature of Ret and you’ll be fine.
Edit: As a disclaimer, I played it with T5/S3 gear. In Season 1 Ret/Dreamstate might have damage issues.