I tried going through a dungeon with a level 110 and 4 freshly made characters, it looks like the xp malus they get from the one high level character isnt worth the time in completion speed that the team gets from the level 110.
Xp looks like its 1/3 of what you are getting when you bring 5 characters with the appropriate level so i went back to this.
This might be because i still have Raf active?