From this source:
" Fixed an issue that could cause choosing Nightmare Mode to not set enemies to Nightmare difficulty."
So .. Does that mean ... We've been killing bosses on what we believed to be Nightmare but ... It hasn't actually been on Nightmare?
Wow Bioware, I'm not sure how you ****ed up this badly.
I knew you'd screw it up because you're new to the MMO market but ... Well, I'm surprised. Congratulations.