4 ultra balls are too many, even with a 3/2 darkrai/absol split but if you chose to run single copies of certain Pokemon, 4 may become viable. Also, a couple more energy switch would be good in the deck since you can easily power up pokemon with the help of the dark patch/energy switch combo. When darkrai was big last season it always ran 3-4 energy switch and in testing I find 3 is a good amount to consistently power up darkrais very quickly.
Hi shiney mewtwo!
Hi shiney mewtwo!