Well, just finished FoV here, and I have to say the entire expansion was very well made.
About the final mission, though...Played through and finished it my very first try on the normal difficulty.
The trick to doing it is to rush AHEAD of the zeppelin: do not stick to it. Take out the ballista towers in two fire spheres, save your ultimate attack for those islands with a spawner/lightning tower in the middle and aim it at the middle, that should destroy everything around it. Once you get the zeppelin bombardment ability you can go ahead and use that on lone ballista towers, or use it on a spawner to leave it at about 5% of it's health so you can easily finish it with a fire sphere. Use your friend whenever possible and save your fire breath for any flyers. You need to conserve your mana so you can destroy the towers long before the zeppelin gets to them.
As for the final fight, it was really the only fight that could hurt my character in foV. But even then once I stopped being perma-stunned by magic blast/polymorph i was able to finish the fight in about 5 seconds. Of course, my character was about level 43, had 100 strength and vit, and was using the Tiger Bite sword with a legendary shield. I crammed the sword with +100 physical and magical damage enchantments as well as a +9% critical rate enchantment on it.
Overkill? Yes. But after the final fight in the original ED I didn't want to take any chances
