Rya.Reisender
Explorer
I don't show monster HP but that still kind of happens due to my narration.It definitely wouldn't be my bag. I think that the tension comes from knowing how close the character is to death and, to that end, hit points help with that. So much so that I reveal monster hit points to the players via their hit point bar on Roll20. Everyone starts getting really nervous when the fighter or paladin whacks a monster for big damage and the bar only moves a little.
My players would go like: "I'm a bit worried, we already did 20 damage and Rya didn't even say that he is moderately wounded yet."