When adding the rasters to the mosaic dataset, the raster will not be imported, just the footprint so there is not going to be a resampling error. I would see if the statistics for the mosaic dataset have been calculated and if not be sure that the statistics for each raster is as well. For specific help with your mosaic dataset, then call in to support and we can set up a desktop streaming session and look at your mosaic dataset with you.