Spare may not give EXP or Grub, but it could be good when you DESPERATELY need to get out of a tight spot. Plus, may not activate as often depending on the Job's role.
Sleepyhead is free healing, pretty rare if the Job can heal themselves. Really good for quick recovery.
Hide may be annoying, but I kinda see it as a win if you're a Job with REALLY low defense. It's part of the Laid-Back charm, too! (i'm biased from my 3ds days)
Slack off conserves MP, which means you can use MORE skills later, maybe even some under "Get Serious".
I have never seen Shan't. I bet it's annoying because the target is knocked out, but it's just so rare...
That just leaves the worst one. The one that I have to deal with all the time on my Switch run.
Bluff doesn't block just HP restores like I thought it did when I first came to the wiki. It blocks MP HEALS. It blocks FOREST AEGIS. It blocks LOVE AND PEACE??? AND it's a 20% chance, which is ABSURD. It sure does make my run a lot harder, since two of my ten party members share this personality. (And one of them is me...)