Does success ever go down?

200 or 2,000? I've put Cromm Cruaich (10k CP), Hard Doppelganger (40k CP), and Elite Doppelganger (60k CP) with just one try.

I thought it was established that the success rate is fixed and is not CP-based, contrary to what the in-game description says? In any case, (and you know this was coming) lets see what JP wiki says.

"同レベルの敵の場合、睡眠確率75％" Or "If enemy is similar level, Sleeping Chance is 75%"

I dunno x.x...I don't see the reasoning behind anything regarding 75% sleep chance if I can just sleep anything with 1cp ._. Maybe it was a beta thing or my music buff effects are stacking the odds. I ahve around +60~