I like the game so far. It has a cool art style and the gameplay actually feels fun! My problem with it so far is there's too little to do in-between levels. Your personal quest is the most fun thing to do but they make you wait multiple levels between each iteration of it. But ... the smaller quests are quite rare so you end up grinding quite a bit. Then again, it's hard to argue with an MMO that has no subscription fee.
Are you doing the world events? I noticed they upped the xp quite a bit several days ago so I am no longer outleveling the hearts for quests. I have not had to do any grinding at all. So far the leveling is going very smoothly but I do the events if they are in the area. Oh and harvesting stuff gives you xp as well so I harvest all I can.