You know armour doesn't affect the legs right?
I always aim for the knee caps, then after they are down, shoot the armour off before you execute them.
I really annoys them to be spending so much on armour just to have it bypassed by the old kneecapping shot.
Oh, and it's a TPS not FPS.
FPS is like CoD... Crappy first person view. TLOU is better because it gives you a Godlike third person, over the shoulder view.