Does dungeon master mode mean that up to 4 players control the party members while another player (the DM) controls the monsters and maybe other things of the environment? This could be fun. Especially if people create dungeons specifically for such things. You could consider this as a type of asymetric PvP.
Unfortuanatly I will never profit from this because I play single player. But it is a good idea.

Prof. Dr. Dr. Mad S. Tist

World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already