The Chimera, the Monk and the Guard

[Rydin]

they never tried out in a different way.. a monk can easily replaced by a drg (as melee dmg function) and the other way around... because they almost fit the same role!

Yes you can do the content with a variety of class setups....
But when it's content you run over and over and over... you will inevitably want the fastest possible way...
If it was content you only had to do once or twice, then you'd see a variety of classes... but knowing you need to spam it HUNDREDS of times... people are eager to shave even a minute off of each time... because in the long run, that can be a big deal