Yeah, I would totally not show an enemy's HP. Health bars without numbers or stoplight are acceptable.

As for the rest - you absolutely don't need to know an enemy's AC/resistances in order to fight them. No one is forcing you to research a random goblin - you can just kill them. Having more information makes it easier to win a fight, but my preference is for that information to be earned through conscious choices (either deliberate actions or how you build your character) rather than given freely.