I am not sure I like either of the rain in your last 2 uploads. On the 1st one I thought it was the water moving and not rain and on the 2nd the loop was to short. Maybe take the 1st one and make the rain come in at an angle?
i thnk the problem with both versions is that you can clearly see a pattern that is being moved. By the random and fast nature of rain it would probably look much better if you prepared 3 or 4 random frames rather than translating a single one... if you know what i mean?
This one is created using an image of rain sliding in from left to right and on top of that there is a layer with rain created with the rain script from AS.
Epic work, moorsel. The rigging aspect of this is fascinating.
However, I notice that the animation is a bit unpolished in places. For example, the sequence at 1:40, the princess's legs keep moving after she's stopped and both of the kids are frozen mid-stride with arms bent. These should be easily fixed.