I can understand if the level requirement on Abyssea is not raised, but what could be done to restore some semblance of balance is cap the XP you get from mobs and chests within certain level ranges like they did with Campaign Battle. The lower levels can still leach, but don't expect to be level 75+ in one sitting type of thing, it encourages more focus outside Abyssea really. This also prevents any conflict with the disclaimer level 30 characters being able to do quests in Abyssea as they can still jump in and do stuff, but the big rewards for the low levels is more of items they can sell on AH for a bit of gil.