My experience with slow rip.
I have a new LG WH16NS40 and an old LG BH08LS20. Both seem to exhibit similar issues. The first rip or 2 seem to run fast, but after that, it starts slowing down. If I pause the rip for a few seconds and hit continue, it will resume ripping at a fast speed again for a minute or so and then go back to slow. However, if I restart or shutdown the computer the "riplock" gets reset and the first rip is fast again.
The LG BH08LS20 has CSS Riplock but not sure about AACS Riplock. The LG WH16NS40 should not have Riplock protection. What type of BUS do you have your drives connected to? What are you sending the data to? You have a bottleneck somewhere.