You not knowing something that you find out EXTREMELY early in your playing career lends to the notion you didn't experience the early game.
Some people only listen to what others have said about gear, others test things for themselves. In order to write up a strategy guide, someone has to be the first to do it. Knowing that INT/MND are most likely related to something with spellcasting is very easy to ascertain. The exact mechanics of it is more difficult. The challenge and lure of this game is to find the correct balances in everything.
This is a formula based game with a great deal of luck involved. As in any game that deals with chance, you try to stack the deck in your favor as much as possible. By taking a job from 1-75, let alone 3 jobs like your character has, you should have learned this long long ago.
Skillups occur whenever action is taken involving the use of that skill could be used.
EVA skill is the chance you will evade the mobs attack. If you get hit, that doesn't mean your evasion skill wasn't taken into consideration, it just means the calculation didn't work in your favor. Because of this, if you are under the cap, you have the potential for skillup, as in anything else in this game. Crafting if you break something, you still are able to skillup, lord knows I wouldn't have hit 100 early as I did without it.
Its a simple game, and by not picking up on consistencies found everywhere in early levels that are there to specifically teach you basic game concepts you are giving us the view that you either are:
A: God-damn stupid to miss so many things
and/or
B: Must have not played the early game