They said they tried multiple class set ups using all classes except for Paladin(obvious because of how useless it is) and they wanted to down it first so it would be obvious that that set up achieved it. I wouldn't doubt you could use other classes for the fight, that is just the set up that got it downed the fastest. Do realize that is basically the best Ls out there, they will eventually be able to down it in any way they like if they choose.