I tend to use a simplified damage system for enemies: 50 for light, 100 for medium, 150 for heavy, etc. However, I've also been experimenting with puzzles and gimmicky enemies. For example, one enemy, Hellfire Leo, must have its mane put out before it can be damaged by most attacks.
I've also been planning to weave exploration and gameplay in future Labyrinths and dungeons. Maybe add a player health system, too.
Side note: I use dice rolls to determine hits/misses, but I also reward clever players with bonuses for not just doing *spams Ice Age*