It´s not unexpected :\
I had this prob with JMB363. If I used one SATA-drive the drive often burned 4x instead of 16x. One time I burned with 2 SATA-drives I needed over 30 Min to burn a SL-DVD.
Other problems can also happen, my BH16NS40 freaked totally out on one controller, stopped writing and let hang up the PC x-times
Note: It´s not happen with every JMB, some cards worked, some not. Firmware was the newest I get for it
The cards which works best for me are older cards with Sil-Chips