Mustadio (again, i'm going off a memory from probably 20+ years ago) had some fairly low hit rate cool abilities but nothing special. Most people went with Chemist for him because they could use Guns and they had all the item effects so you could just run around phoenix downing people vs. trying to wait for Revive casts from whms.
You pick up concentration from Archer which changes the hitrate dramatically (been awhile, I think it doubled? For abilities? Or something, and changed regular attack hitrate to 100%) and then you pick up the weapon break skills from Knight (use that as his sub from Engineer) and it changed the success rate of the breaks to fairly high levels if not outright 100% depending on level.
Will have to look at the WOTL stuff for PSP; I'm pretty sure I don't want to give SE 60+ for a barely graphical update.