mor dhana is just exciting because you haven't spent 100 hours running around it already, and it's night time all the time. The monsters are much higher level so youc an't really "do" much there other than try not to die, and chances are, you will fail at that task. in cb1 and 2 all we had was limsa. grid and uldah areas were "amazing" because we hadn't been there and didn't spend much time there. Case in point: ifrits cauldron. at first it's totally awesome, then it's a pita and you don't bother spending much time there unless you're going for ifrit prime battle or to farm.