Ugh, what a nightmare. I spent a few hours trying this battle over and over. Finally, success!
For me it was a jump to the left (and then a step to the right...) Nevermind.
Anyways, It took some doing, but if you get a creature out there, to draw attention, you can pick off each soldier, healer and mage one at a time. Maybe I cheated, but I'd kill one or two, then save, think about my tactics, kill another one or two, save, until I got them down to the Divine and Zandolor. After that, I had the ghost and my summoned creature. I took out the Divine first as his rush attack is a pain.
You have to keep moving, and stay away from the Divine's rush attacks. This is why I needed so many potions.
Was the battle hard - yes. I had to turn down the difficulty level, and I've NEVER done this in a game. I do think this fight was just a tad over the top. It should have been more difficult, but not near as impposible as this was.