Quartz
Hero
I take your point. What's not fun for the players is grindy combats that take a full session (or longer) to resolve. What is fun is a dynamic combat with a sense of genuine peril. At higher level, a character who is dropped to zero hit points is usually back on their feet by the time their turn comes around. Only now they're mad!
If you have your canonical four player party and your monster is dropping two of them every turn then they're not going to get very far. And dropping three is TPK territory. Now, if you had a six or eight player party then that's another matter.