MAKING DEF LIKE ATK

Depends on the engine you're using and the work you put in.

With a default database and rpgmaker vx ace or later:
defense is subtractive, but easily controlled by the damage formulas you enter
default formula is atk * 2 - def, which makes attack and defense stats scale equally, but if defence is double attack, then no damage is done.

resistances are multiplicative:
element rate of 10% means you take 10% of normal damage
element rate of 0% is immunity
element rate of 200% is double damage
etc

Now lets look at some non rpgmaker systems.

An armor rating with 2 numbers... (based on roguelike TOME)
light armour (leather) with 5 / 25%
light armour (mithril) with 40 / 25%
heavy armour (plate) with 35 / 50%

The first number is the maximum damage absorbed, the second number is the damage resisted.
A wolf hits for 8 base damage - this would be reduced to 6 by either light armor, or reduced to 4 by the heavy plate
A dragon bites for 200 damage - the plate reduces this to 165, while the mithril reduces it to 160 (in both cases the damage reduction limit is exceeded)

Diminishing returns
Attack and Defense are converted by a formula such as square root before being compared.
May convert character stats and equipment stats seperately and sum afterwards to make equipment progression more important.

example from an MMO:
first 700 points of attack are worth 1 attack power each
next 1000 points are worth 1/2 a point each
remaining points are worth 1/4 a point each

So that continuing to min/max into attack would still improve damage dealing ability but by lesser amounts, while a small investment in defence or HP would improve survivability considerably.
(Said MMO had equipment for attack, defence, healing or HP)