Quelle, as I agree with some of your points, I disagree completely on the rest.
As my post above yours explains the rationale of grazing hits, your idea that all character builds should be inherently different when it comes to hp is completely off base.
If you are wearing leather armor as a rogue, and your armor class is super high (rogues can get some of the highest AC in the game), chances are you can tank almost the toughest raid bosses. That being the case, if you were in my PnP game with high AC, and we discussed and agreed upon grazing hits... you better believe if you're hit by a grazing hit in leather, you're going to take a lot more damage.
That being the case, and after reading what I just wrote, I want to take the side of the OP. I would like to change Grazing hits to do more damage to cloth and leather wearers, and less damage to people in plate armor. Realistically, thats what should happen.
CHANGE GRAZING HITS!!! SQUISHIES SHOULD WEAR PLATE!