Like most of you, I have a 9400M GPU macbook and the FPS is too slow to play. But at last weekend, I did below actions to make it playable and two days, I have 13 lv, and killed Ske King with very easy, no FPS issue.
1, Keep the default setup, you may have 10FPS, but now is 800x600, the words are mess.
2, Choose the game to be played in window. This will make the FPS to be 20 in big map, 25+ in general maps and in some case, it is 30+ to be 40. Even in the action during killing Ske King, you can feel the game is smooth.
This method makes the every word clear in the screen, but the dialog may be too small. But these words will be red by the game, you just need to listen, no need to see them. So by using this, you can play the game.
Another thing, you need to pay attention is the server delay. Take Wizard for example, when I click the mouse for several times, you can see the sword is moving, but not magic actions out. This is caused by server delay. Please choose a good connection server first.