I came across Create Thrall when I was making my character for Curse of Strahd. I decided to go with Goolock for thematic reasons, and made a list of every way to incapacitate someone in 5e, even knowing the campaign doesn't get to level 14. Hypnotic Gaze still stands out to me as the clear winner for being recyclable and also a really strong ability on its own, as well as not (RAW) breaking Sanctuary.
I still think Goolock is weak (this can't affect non-humanoids, which I find a little disappointing), but nowhere near as weak as before. Honestly, this could make a GREAT villain.
Sorry, I meant rounds, not turns.
Anyway, my figure comes from the DMG, which recommends three rounds as the average length of a fight. Your mileage may vary, but that's usually accurate in all the tables I've played in, and the few I have mastered as well.