definitely random. I've been 50 for a while now and I run BT hard mode every day for the daily. Sometimes for like a week in a row I wont see anything for my class or anyone else in the group drop.
I don't have any level 50s yet, so I don't know about Hardmodes, but regulars have always been based off class for me in my experience. Honestly, I always though it was really cool how the group influenced the loot drops. I guess that's not always the case for everyone. If I'm bugged, I hope it remains so!