Is using a shield effective?

Solution 1:

It turns out the shield is, as @GnomeSlice described in the comments, worthless. Also, I stumbled across an article with a quote from Masaaki Yamagiwa, one of the producers at Sony's Japan Studio.

"There are shields in the game. However if you're always standing back and guarding, you'll die very quickly... We wanted these encounters and battles to be so intense that If you just stand and wait, you'll get overwhelmed and killed right away. We wanted to encourage players to not hide and wait, but instead be more aggressive and pro-active in battle."

In other words, put down that shield and toss it into a fire.