While this may be a bit of a bug or intended I am not quite sure which, BUT while in Dark Apotheosis (Glyph of Demon Hunting) Our fear turns into 'Sleep' with a sleep restriction of 1 target sleeped (slept?) per warlock much like fear. That being said, if I sleep something and swap out I can also fear something as well so in theory I could CC two targets for at least 15 seconds easily (10 seconds in PvP not taking DR or trinkets into consideration) A bit of a set back I have noticed is that if you take blood fear, for the instant cast fear, then even 'Sleep' becomes Blood Fear which is a little bit of a bummer but I can deal with having to cast sleep if it means that we now have 2 types of CC. I am curious if anyone else has noticed this and what their take on it is?
tldr; DA turns Fear to Sleep, You can Fear a target and Sleep another target at the same time, if you spec for Blood Fear, then BF overrides Sleep and you cannot use Sleep