Technically it's still a 26 defense if you don't include the shield... but it's still powerful because you can cast only 2 lightning and hide behind a shield because each lightning hits 4 times with 40 damage (40 Dmg x2 lightning x4 hits = 320 magic dmg) and you stand behind the shield and only take 1 damage. Moreover - shields in the game are broken because if you raise a shield you will get x10 DEF stat which means if you have only 10 DEF stat of character it's 10x10 = 100 DEF.
I'm already personally tired of goblins running around with a wooden shield because they're pretty hard to penetrate sometimes even with a halberd at the start because they have too much DEF stat even without blocking and 100 HP. I mean - you can kill them of course especially in an open field but it's a lot of running.