That disorient is a pain in the butt if you don't constantly stop the cast. I'd stop every cast I could - it's a very fast animation and lag would let some through - and spam interact with target to reface my disoriented shammies.

I farmed BT to cap the rep (and get the loot 100k guild achievement) and would drop all my tank and fire pets during that part and lust to get past it in the end. I never finished BT alone, usually stopped at the second to last boss and haven't been back in the last three or four weeks since I capped the rep. When I did clear the whole place it was with a friend or two and then it was trivial.