on this subject, I was also having a similar problem with pixelated depth/normal maping. I've found a work around by simply exporting the created colour (difuse) map from 3DC and then converting it to a normal map in photoshop using Nvidia's excelent DDS plugin for photoshop below:
developer.nvidia.com/nvidia-texture-tools-adobe-photoshop
You may need to change the image into a bump first (grayscale mode and contrast/brightness adjustment then back to RGB mode). You then import the finished/'normalised' map back into 3DC via Textures> import> normal map.
very happy with the results, hope this helps anyone.
