I thought this was a characteristic of all silnylon, even in pristene condition. It can't hold up to the pressure exerted by a large fast moving drop hitting it. The misting you experienced is exactly as I have seen it described before. If you search "+sil +misting" over on TLB forums you can find all kinds of threads about it. Here is a quote from some guy who goes by the name "Just Jeff"
"From what I understand, any material is only waterproof to a certain pressure. If you subject the material to a higher pressure then water will come through it. Silnylon just has a lower pressure than some more "heavy-duty" materials, but it's still "waterproof enough" for most hiking uses. I think this is why some people report misting in heavy rains."