Well I figured with the recent patch and tweaks to CoF that this would be fixed and I would have a fancy new Dungeon Master title today, but it is still broken. So many frowns.
For clarification, after clearing the instance and finishing the last boss the chest will spawn. However the instance will not finish out, which is preventing me and others from finishing off the CoF explorable achievements. Anyway when you guys do get around to fixing stuff like this(and the door in Arah Jotun which you all ready fixed, if it was even broken we might have just been super unlucky with that one) you should try and make an effort to point out that issues like these remain or have been fixed as it would be helpful in the future.