My favorite map is maybe Shadow Wood, but there are some others I like a lot. As an episode, it's clearly Shadow Wood.
As for the Heresiarch's HP, see <!-- m --><a class="postlink" href="http://www.ravengames.com/hexen/hexen_bestiary-03.html">http://www.ravengames.com/hexen/hexen_bestiary-03.html</a><!-- m --> (but in KMOD he's got a lot more).