First of all, my point still stands that adding another mechanic to fix a broken/unnecessary one is bad thinking. That's the main point of my posts thus far.
About realism then:
I know everybody will think this is crazy but...Halo is not that unrealistic.
It's like this: firstly, the default for everything is reality as we know it. Right? I mean, that's pretty much what default things: the way things are normally. A simulator attempts to mimic that reality, for example. (I know I'm not being the most clear; I'm trying to be).
Secondly, games are about balance. Life isn't always "balanced" and thus is not always "fun." Fun is never fun when it isn't fair, to which being balanced is imperative. You must be balanced to be fair, since the two words cover the same area.
In a game then, we have to take selective parts out of life -- out of the default of reality -- to cut out things that make life unbalanced. Interestingly enough, it appears, the less "stuff" we have, and the simpler things are, the more fair the game becomes.
If we have two dudes with swords, and these swords kill in one hit (we could go even simpler than that, but whatever), this would be perfectly fair. If I hit him first, he dies. If hits me first, I die. Nobody can complain in this situation.
Unfortunately, that is boring, so we start letting some reality back in. Now a sword can only kill you in one hit if it cuts your head off, and say it can only do that if you pull the sword back above your head to give it more force. More interesting.
Now we give the two guys guns. Let's make up a gun. It doesn't matter, it's still acting like reality. My gun shoots hamburgers that explode. That's fine. It doesn't kill balance with the game, and, believe it or not, it's still realistic. How? Because all I did was make a bomb that looks like a hamburger, the fact that it is a hamburger is unimportant because being a hamburger is not functional. It's just a skin we put over something that explodes. This requires some abstract thought here. It doesn't matter that we don't have exploding hamburgers in real life. It works in the game; it follow reality in all the ways it needs to; the concept is predictable (as long as the person knows the hamburger will explode); and our game is still balanced.
Now we do something strange. Our player knows that the hamburger explodes, right? So he shoots the other dude with a hamburger gun and it explodes on contact. Unfortunately, nothing happens. The explosion has only take 1 % of the other dudes health. We would all agree that this is bad game design. The hamburger gun, then, is useless. We might as well use the sword right? Exactly, so nobody use the hamburger gun now. Why is it bad? Because the explosion doesn't do what explosions do. "But it's a hamburger!" So what? We now know that hamburgers explode. "Yeah, but now we know that explosions hardly do anything!" Exactly. The difference here is that the hamburger being a hamburger doesn't affect gameplay. Not doing anything to your opponent with an explosion does.
End of story, btw. The following is yet another example, basically.
So in our example, nobody uses the hamburger gun until one of the guys looses his sword. In desperation, he goes and grabs the hamburger gun, and shoots a hamburger at his opponent. Then something unexpected happens: this time the hamburger kills the dude instantly. Why? Because "to make it more exciting" we made the gun more unpredictable. Except, this isn't fun. It isn't fun because it isn't fair. "Oh but it is fair because it could happen to you to." No. Fun is also about something else, that I talked about earlier: control. If I can't control what my actions accomplish, then what I am doing is not fun. The further a game gets from the reality of "My actions cause these reactions, maybe with just a little bit a variance, depending on some factors that I am capable of being aware of"; the further it gets from being fun.