I loved the Oz scenes tonight! There was so much speculation about who would be Dorothy, the Wizard, etc and I don't think anyone guessed Zelena was Dorothy or Walsh was the Wizard. Other than that, I agree that there seems to be a lot of retconning going into this storyline.
I was a little let down by the Zelena/Regina showdown. Zelena has the power of the Dark One behind her and THAT was how she went about trying to get Regina's heart? I guess she probably didn't think Regina would know what she was after but still, giving your enemy 8 hours to prepare a defense seems a little odd for someone who thrives on the element of surprise.