Although that's what 100% resists would look like. Health cost of making an attack - effectively 0. Most powerfull mechanic in the game by default (damage resistance, or rather, resource free reduction in health cost per attack) and needs to be kept in check and only moderately available, otherwise you get that.
Not sure how Gaan'Telet giving you potential extra resources (moot, really, only extra thing is the sensation stone tbh), and Drac (again, I don't have vamp unlocked so I have no clue on Vamp worshiping him being possible) figure into it...
Also the status of the Vamp being a post-game bragging prize as fara sa balancing is concerned might figure into it as well.
Also, Horatio's damage is pretty mediocre for a boss, he's like a really souped up SMM with res on top of it. How much more lifesteal could you get in a regular run?