Like a lot of this, pretty simple and old school, which makes me scratch my head at adding 4e's abstraction of auto "aura" damage for the fighter.
Hitting people you understand-- you hit the guy. Missing people you understand -- you missed.
This thing where you miss but you still hit is a gamey abstraction that rankles. It emphasizes too much the abstract and artificial nature of the game, rather than pushing that into the background.
People want to know what their character is actually doing in this fictive world. Putting abstractions like auto-damage, even on what everyone will term a "miss," violates that sense of actually doing something in a world.
I know you *think* you can "cover this" with a brief bit of explanation -- "your attacks are always close calls" -- but you sort of went wild with that in 4e, putting cutesy explanations for lots of completely abstract gamey mechanics, and it really separated people from the idea "my character is actually swinging a sword."
I know that Hit Points in D&D are supposed to be an abstraction to begin with. But a lot of times, people would like to forget they're a pure gamey abstraction and really imagine each point is causing physical damage to the opponent, and not merely a "loss of energy and vitality."
Stuff like auto-damage -- especially being so prominent, on every single miss for a Slayer -- really puts far too much weight on this abstraction, and never lets it slip far out of one's mind.
The concept of the Slayer is fine. Nice and simple. But why not just give him +3 damage on a hit or something? Why go down the pure abstraction/"we'll cover up gamey kludges with brief explanations that are sort of hard to buy and anti-immersive" path again?