Never seen world strongest kick in effect in game (Dungeon Fighter Online gold), but it seems you are way too vulnerable during the whole thing, being stationary while enemies are free to peg you every which way. Obviously we have not seen many videos of it, only one we found was Nexon 2 second clip on the subclass promotional videos.
Witch passive is mediocre to us, because the buff only occurs on a sleeper and lasts 5-6 seconds on a tier 2 spell in DFO. The 15 seconds on tier 3 is more useful, but you do not spam those quite as often. There were some questions in game (Dungeon Fighter gold) if the buff time was even extended by new sleepers or if it just stopped and had to be re-proceed. You also have to weigh if you want to spend 150 points on something that only procs on sleeper successes.