Playwise, I am unable to give feedback, as I don't have any current groups that are at the point between Wizards of Morcar and Mage of the Mirror. As a game master and Quest designer, I can say it's awesome! The idea alone of bridging the gap between the European Morcar and American Zargon with story, instead of just interchanging the names is a fantastic idea. The Epilogue is not only enjoyable, but tends to tug at your heartstrings at times. A lot of it would make a great prequel Quest!
The story is just great. As for the Quest itself, having the mercenaries (men-at-arms) pose as outlaws for the Heroes to battle against is a really nice change from the regular monsters. It adds a little more depth to the HeroQuest world. The caption titles for each note are a fun addition for a game master to read. It's a little something extra that brings some fun and makes the Quest seem more like a story playing out, rather than just another fantasy board game Quest.
Hopefully someone else will be able to give you some more feedback, as well as some on game play. Otherwise, some time in the future I will have some feedback on game play that I will surely post.