When to switch from reck to one handed spec?Follow

You should already have One Handed Spec. irregardless of whether or not you have outgeared Reckoning. Even then, it's only ideal to drop reckoning if you want to optimize your raiding tank. If you still want to do instances it'll probably be worth it to keep it.

I would say you wouldn't drop reckoning until you are beginning T5, by then your avoidance should make it almost pointless. It will almost never proc because you won't be getting hit. Then those points can be used to further your mitigation in other talents.

Looking at your build, you don't really need Precision or Pursuit of Justice yet, dropping those for One Handed spec will probably help you more. Then grabbing them back later when you get to the progression that I mentioned earlier.