So yes this is a completely useless bug.
But if you don't want to use your HS this would be good.
So I did halls of reflection. And wiped.
When u die in icecrown you get a flying mount to get to the instance with.
So I was going the wrong way ( to wintergasp ) and suddenly I dissmounted.
The battle was begun and I pressed cancel if I wanted to join , I was ofcourse dead and somehow I got teleported to dalaran , full hp & mana and without HS been used.
Hopefully this will help someone but as I said for me it's completely useless :P
Enjoy
-IggyZ