I hope you don't mean that you're level 28 and still in Krokotopia. At that level, you could be in Marleybone, possibly even Mooshu, if you avoided the side quests. Anyways, I feel that Krokotopia gives the proper amount of experience for the level range. You aren't going to immediately reach level 95, so you may as well continue questing.
Also, I advise against power leveling in a dungeon because you miss quite a few spells from doing so. For example, let's say you power level to level 48. Sure, you have your rank 7 spell, but you missed the spells given for completing Krokotopia and Marleybone. For Fire, that would be skipping out on Steal Charm and Scald, respectively.