The buffer/speed issue at around 10x is likely due to a bug in ODC. It is suggested to use ImgBurn to write the medium and still obtain a write graph; should this not help, then it is likely an issue somewhere else within the system.
And as Electrox3D suggests above, the LiteOn drives are not the best at writing to BD-R media. It makes me wonder if a newer Pioneer or LG would do a better job at writing to them, as the LiteOn drives seem to have a problem producing good [equivalently good] quality on anything besides MEI/Panasonic media*.
*: Other media may still be well-written by the LiteOn iHBS drives, but the MEI media was the first to cross my mind as being notably good