Not sure if you all were aware of, but I noticed this in my play through last night.
Initially, i was a bit frustrated not knowing how many more rounds it would take until i defeated an enemy, because theres no traditional energy bar.
But, if you look at the number in the blue shield next to the enemy, it does go down as the battle goes until they're defeated!
What?
Are you sure you're not confusing that for something else?
The blue shield indicates how many hits they can take from a weapon they are weak against until their shield breaks which allows you to attack them with higher damage.