I just joined a "heroic" siegecrafter blackfuse fight with about 14 people and i was assigned to belts bc i offerred to do them.
I got my mine add to about 10% and instinctively started spamming my fel flame. However, when i started casting fel flame nothing came out. So, i started casting anything else i could think of and i did not kill the add before it got through the belt.
I am a 583 lock with US 125 kills of heroic bosses in MOP. I am dumbfounded atm.