should work.
i have a late 2013 MBPr works fine with OS X 10.10.1 and TP 2.7.1! I use the old Audio2 MK1 sound card. Also without problems.
NI recently updated the drivers for older hardware.
" Updated TRAKTOR hardware drivers for Mac OS 10.9 and 10.10 If you are currently running Mac OS 10.9 or 10.10: There is an important new driver update available for your TRAKTOR KONTROL S4 MK1, AUDIO 2 DJ, AUDIO 4 DJ, or AUDIO 8 DJ. These drivers fix an issue which occasionally caused the hardware to disconnect. We strongly recommend this update to anyone using these TRAKTOR products with Mac OS 10.9 or 10.10 to ensure the best possible hardware performance. To install the latest driver, please follow the link for your device and select version 2.7.0 to download. Update TRAKTOR KONTROL S4 MK1 Update AUDIO 2 DJ Update AUDIO 4 DJ Update AUDIO 8 DJ If you are currently running Mac OS 10.8 or lower, please disregard this update. “”