1. Yeah, definitely less reliable. But with curse on him and reap the forsaken (which I felt like helped with sleep post curse: could just be conformation bias) I felt like my odds were usually pretty good going for a second one. Was honestly very surprised my first one failed, and didn't really have a better alternative without enlarge in the moment.
2. I was talking about the vanquisher here more than the sleep duration. I really didn't want his ally getting in and waking him up, and the vault delay means I couldn't really wait for the vanquisher to go down before initiating. Could have summoned into the sect hall in hindsight though.
3. Vault has great lag. You'll almost always get the first command after vaulting someone, though sometimes their wimpy can save them depending how pulses line up. That's the exception not the rule though.