The 1st Boss is weak toSeriously messed me up.Wind. But Aero is a Level 2 White spell. I really should have levelled White Mage to 2 on my Black Mage.
The equipment is a bit hard to get a grasp of , e.g. with a B rank in Armor sometimes robes are better (at similar cost) , sometimes armor is, with an A or S rank the actual Armor is always better.
Doesn't seem to be any disadvantage for equipping something even if you're rank is E though, so equipping a Shield is always a good idea unless you're dual-wielding/two-handed. Unless there's a hidden penalty that I'm not seeing.
I believe the stats go down if you aren't suited to the armour/weapon, although sometimes even with the penalty you can still end up better off.