My intent was for the poll only to apply to melee damage on miss, but the poll options turned out too long.No option for 'It should be melee only.'
It's certainly not a balance concern. As far as believability... hmm. I can see ways to describe it, like "you're skilled enough to always score at least a glancing blow," that don't break the narrative. The explanation given in the text, however, is extremely weak. A "near miss" should not be doing hit point damage, because of this simple principle so often forgotten by 4E:
Anything that does hit point damage can kill you.
Period. No exceptions. If it does hit point damage, it can kill the mightiest storm giant under the right circumstances. The "near miss" explanation ignores this principle. An axe whistling an inch over your head might scare you, but it won't kill you*.
I think what really bothers me about the Reaper ability is that it stinks of something that was conceived as an abstract mechanic (fighter deals damage on a miss), then given a throwaway justification and put in the game. 3E had too much of that. 4E had way too much. I don't want to see it in D&DN.
[SIZE=-2]*Yeah, yeah, the guy has a heart attack and dies of fright. Explanations like that are funny, but they get to sounding incredibly stupid when you have to apply them to four kobolds in succession. And we're not all looking for that kind of comedy, anyway.[/SIZE]
I don't see a problem in "miss" damage killing an enemy. Nowhere in D&D I've seen a definition of "hit". As far as I can see, hitting just means delivering an amount of damage that reduces the enemy's HP pool (and HP are vague as well). Damage on a miss just means that your enemy will never avoid your attack without expending some resources, and killing on a miss means that your Reaper will never "miss" the chance to deliver a killing blow.
IMO it's balanced (math-wise), but not believable. I understand what the designers see in it: a simple, mathematical mechanic to make the Fighter deal commensurate damage (commensurate with the idea of a Fighter being a bad ass)...but I believe that a mathematically balanced mechanic can also be made in a way that has a believable explanation (fluff). It takes more work, but it can be done...and in this case I do not believe the work was done as far as it should have been.
I don't like it at all...it wrecks my willful suspension of disbelief. In my brain, a miss means a failure to deal damage. If a creature takes damage (of any kind, for any reason, however it is defined), it somehow got hit. Therefore, the attack was not a miss. Therefore, my disbelief shatters.
Maybe I'm "doing it wrong." But that's how I'm always going to do it.