Darkrai is still in ubers because he is still good without dark void but he learns hypno that has something more right and you can take it with Darkinium z / Firium z everything depends on what you want. It is an option for Magearna, for example, but it is better as it appears in the forum. This mon can be abusive against stall above all. The strategy of sleeping seems easy and in a free turn it is Nasty but the result can be lethal. The damage caused by his ability is also annoying if the opponent is asleep. In ou, it would be ridiculous in my opinion. It is true that you do not see much but with a reduced set and knowing its function is dangerous.