I believe it is magic and can be dispelled by priest and pallies.

The priest are right before the boss and they always hex my tank, I wish it was one of the shaman. The shadow hunters in ZF did they same exact thing but it was very infrequent as compared to LBRS which seems non stop. I can bubble out of the first one but seem to get hit with another instantly.

Edit: I'm guessing ultimately I just need to be able to take down the priest quicker which will only come with more levels. Maybe I'll give the other 3 instances mentioned a shot. I never really did the rep grind on my other 70's because I hated pugging but I can already see that running the same instance over and over is going to take a toll on me. In fact, I already made a new 5 man team to play around with, lol.