I I have like 3 to 4 builds depending on what you really want.
You said you want to grind and run instances but you want to PvP. If You want to PvP effectively it has to be an arms build. Otherwise you'll die to a holy priest that knows what hes doing, because you cant reduce his healing percentage without mortal strike.
But if you're an arms build you cant grind mobs effectively. But to be fair you can probably get into any 60 dungeon as arms dps, because none will notice or wont care. BUT that's not factoring in the fact at 60 every tank is really a fury warrior trying to get his pre raid armor by cucking other dps wars.
Going from fury to arms with my shit max stat green items, I went from being able to potentially kill (by rng) 3 like level mobs. As arms it's not nearly as slow as prot, but it's definitely not shining for me at all in PvE atm.