I'm not patient enough for the devs to ask for input on the AC thing . . . let me start with this idea.
People have differing opinions on grazing hits, I personally don’t mind them and thing it as a system can be used to balance certain AC situations.
Armor versus pajamas is one . . . what’s the real incentive to use armor and shield when you can splash monk and get similar AC yet do more damage and (I think) put out more threat? Shield blocking DR is wonderful but you need to generate threat in order to keep agro. The threat advantages of wearing a shield is artificial but needs to be there, but it needs more of a defensive bonus.
Enter Shield Mastery. It was a good idea . . . giving shields a distinct advantage over pajamas but has had some spill-over effects. I hope and pray that it was never the intention of the devs that SHIELD MASTERY WOULD GIVE FAR GREATER OF AN ADVANTAGE TO CASTERS THAN IT DOES TO MELEES. Completely divorcing shield defense from AC is a bad it for that above obnoxious reason. I don’t think the devs intended on that being used by casters to become even more over-powered, I’m going to assume their intention (which backfired) was for shield tanks to be in vogue. In order for that to happen AC needs to be the key to defense with shields benefiting this.
To balance this shield mastery should REQUIRE and ACTIVE defensive stance be enable in order for it to work. Combat Expertise of Defensive Fighting should count for this purpose.
So . . . where was I . . . oh yeah . .. . grazing hits. Getting hit on a 13 for some damage in Elite Content (alledly in epics as well) is the balancing mechanism that some D&D purists don’t like but I don’t mind. I think it makes a little sense, I rolled with a punch, avoided most of the damage but still got hit. Use this mechanic, leave it in the game, but lower the to-hits in higher level (epic) content so a target’s AC is still relevant.
So how does this work regarding Armor and board tanks versus Pajama guys? Have your actual ARMOR (maybe natural too, not so sure about that) bonus apply as DR on a grazing hit BEFORE any other damage mitigation is accounted for. If you have a shield (I guess the wands and Tempest will need to be included) equipped that gets added in as well.
A Pajama monkey will have 8 armor bonus max plus 4 from a shield wand, giving him 12 DR that could apply to grazes. An Armor tank would have about 25+ DR plus their normal static DR and then shield mastery to protect them from grazes.
Grazes will hurt a pajama monkey a lot more than a guy in armor, that’s the balancing mechanism.