the only argument i would have to make for tough dungeons, is that only if its not for leveling or tied to MSQ progression, (which sadly rules out all the level 80 dungeons so far), i would generally love to see some more challenging dungeons thrown into the mix overall since i find dungeons to be very easy in a way that it allows bad habits to be fostered, but i can understand that its best to make the tougher dungeons optional and slightly increase the difficulty curve of more later level dungeons overall.