Agree on both points, the ending dungeon was fun but the actual final boss felt pretty meh. The other thing that bothered me in the final, final fight was: I just spent a bunch of time getting the best weapons and all sorts of special upgrades and... nope, you have to fight him with this one bow thing which is the same no matter what you do. Why did I spend all that time prepping?
Did you do the chamber under the maze (far northeast corner of the map)? Now that was a fight.