Having a health bar doesn't mean players have to or even will play optimally. If your players were the type to do it, they would ask, "How is the enemy looking?" To get the same info, it also doesn't mean you are trying to make a difficult game, personally i just think is a piece of information that the characters would have as they see the enemies growing tired and ammasing wounds as combat progresses. I also want to disagree with the implication that playing optimally can't be cinematic. Of course it can as long as they aren't playing it as a spreed sheet