Thanks for the answers and clearing it up for me.

It'll take me time to adjust from the tanking I'm used to, but eventually I'll get it done. I just find myself thinking "Take as little damage as possible, you're not a dps" too often. As my friends say, "Just let the healer cover your health for you."

Maybe I just need to tell myself to treat shield oath like a cooldown, using it only when needed.