The armor lacks normal defense, almost everything in the game does it. Hence you want to stack it on both armor pieces. I think only skellie armor does normal+shadow, though it has fire weakness. The helm might compensate nicely though. Other options would be vog coat, mad bomber coat, volc demo coat. or suits, rather than coats. Damn vog brainwashed me.

Shields only apply their defense when active though. Can't see if you realize that through just your post. A shield is like another player you use as a human shield, it has its own defenses and resistances besides a health bar and will take more hp damage (ie break easier) when it's not resistant to the damage its being subjected to. As such, unless you shield everything perfectly, you'll be shocked just as hard if you take electric damage as when you wouldn't have the shield equiped at all. Only your armor and trinkets can change that.