I was able to do it in one try, but the battle was definitely not easy. Spent the first few rounds healing myself and placing traps. Wasted most of my traps because I had to heal myself with a scarecrow. Went back to placing traps and occasionally healing myself. And finally was able to blade and cast a decent spell to kill the adds. Once it's just you and the boss, it's easy and quick. The battle took me a bit of time, the two ice mobs constantly shielded before I was able to bring them down.
My advice is to load up on scarecrows and empowerments. Use empowerment whenever you can and then use scarecrow to heal up and do a little damage. Be sure to save a blade or two and some traps for the boss once the adds are dead. You should be able to one hit the boss with a decent Von, a blade or two, a feint and a trap, once the other mobs are dead.
its not to hard to get that spell in one try i only used 2 buffed scarecrow on the minions then i used a buffed dr von on the boss with a regular feint and a plus 80 feint and killed the boss in one hit