Yeah I was thinking about that... it's kind of armor but kind of a weapon in a way...

In the game I think it's defined as armor, I was considering things you that have in your hands as weapons. Whereas armor is something you put on and don't have to "hold" I guess. I was thinking Shield is equipped in a weapon slot, when saying that "shield is a weapon".

Anyway, the point is Sentinel is a class and won't be changed.

I think the bigger question here is... if you leveled Glad / Thm / Con why wouldn't you equip a shield?