Has anyone else been in the LFG queue for a heroic and once a group is found, you accept and are then summoned into the middle of a boss fight? It's happened 2 or 3 times to me. Typically, half the group is dead by the time I join so it's very difficult to provide any real contribution to the fight. It usually just tacks on an unwarranted repair bill. For what it's worth, I always queue as a healer.
Is there any way to prevent this? ...telling me not to queue is an unhelpful response.