its still a big boon to basically take up most of two enemies turns, and the dc is always that of at least the highest level the which can cast, usually a dc 15 to start. Also, a sleeping enemy could be just taken out completely by a coup de grace before they have a chance to wake up, and a smart witch will easily take advantage of that when targeting.
It's not so much the ability itself I have a huge beef with, powerful as it is, it having that in combination with all the other many things they can do with other hexes and as full casters.