When you go up in physical level you put your points into the areas you want(Everyone knows this), but Class Level only uses so much of each stats points. For example:
Level 10 Gladiator, Level 16 Physical.
If you put 57 points into VIT. Anything past 50 points is redundant. Level 10 class I found out only uses up to 50 in one stat. If you surpass this then those last 7 points are completely wasted.
This is a way to stop people from putting all their eggs into one basket. Maybe someone can experiment with Levels 1-9. Best way to experiment is with VIT or MND(guessing that's the one that gives MP?). Something physical you can see increasing.
I think it would be great to know how much we can have into each stat at each level so you'll be a better character. I hope this makes sense.