There are a lot of things that engines do that is "normal" but not good. The early GM LT1 engines used teflon valve stem guides that tended to wear out around 15K, lots of heads were replaced in the mid 90's for something that was "normal". In your case it appears that your crankcase ventilation is not adequate and that's causing the issue. Again this could be "normal" but not good. I don't know off hand what your engine uses for ventilation but I would look into it to make sure it's working properly.
Oh and all engines create blow by... there is nothing that you can do to prevent it unless you can make a piston ring without a gap, and totally seal the cylinder wall to ring area no matter what temp the engine is... the only option is to relieve the pressure in the crankcase and to help keep the oil from getting contaminated its good to get fresh air circulation as well.