Actually, the job advancements are:
2nd job > 11
3rd job > 20
4th job > 30
The tests were a PAIN to do, now they're a lot lot lot lot lot easier.
I'll get the tests later.
Also, about the skull. Well, my old Lass used to be level 31, and I loved to use the skill (:x), however, the people I normally played were 5x~6x, even 7x, so they survived. Still, the skill easily kills someone 15 levels above you if you get it right. The balls will only get the person stuck for a moment, after that they can just run if you don't do anything.