If you do 2 Ninjas and 2 Sages, you don't have to. I forget exactly what level my party was at -- I believe it was somewhere in the 50s -- and I beat it. However, I also had a load of Shurikens for the Ninjas which was critical, and when I did beat the Cloud of Darkness, it came down to the wire. It was kinda like a walk-off home run, if you get that reference.