I can use your own logic: Why does a guy who learns Fire(5) and Earth(5) magic can have the same efficiency(with Fire spells) as a guy who focused only in Fire(5)?
The one who specialised in Fire alone should be better at it, isn't it? As of now it is not.
This, I don't really see as a problem. Frankly, being a mage and picking only ONE school is not a good idea, because if you run up against enemies strong to that element, the mage is going to be a load in the fight. If you're deliberately building a character willfully ignoring that, it's silly to then turn around and complain.
If you want to think of it in other terms, a mage who spends points on Fire 5 and Earth 5 will be great at those schools, but will have fewer points to put towards other abilities. A Fire 5 Only mage can put those skill points to use doing other things.
Getting your stats lowered to the point that some of your inventory becomes un-equippable doesn't (or originally didn't) cause the items to unequip back into your inventory; they just become hidden in the slot and will reappear there once you met the requirements again.
I can confirm that having your stats lowered definitely DOES unequip the item into your inventory, it's happened to me repeatedly.
