Howdy,
I've thought about these suggestions, and found that when reading the post, it's important that any changes suggested do not in any way change other play styles, so with that in mind...
Suggestion #1
Physical armor = DR %, that is to say that any armor that is a physical, shield, full plate, and also the +5 are totaled to give you let's say 5% for every 10 points. What is not totaled would be monk wisdom ac, dexterity, and similar nonphysical bonuses to armor.
So wearing +5 full plate (13) and having a +5 tower (9) shield would equal 22 points and then 10% dr. This is a rough idea; don't let the % amount cloud your thinking.
I would make this stack with DoS and SD prestige class stances.
Whether or not the % damage reduction would hit before or after the value DR (adamantium for example) I'm not as sure of, but perhaps a complete shift from value DR (-/3) to % DR might be in order.
Suggestion #2
Parrying and Greater Parrying = more like displacement
This has bothered me for a while, in combat a parry is not just someone missing you, it’s you deflecting their blade away from you all together with your blade. I would make this like a blur or displacement (stacking of course) but not able to be removed by True Seeing, it should also on a successful parry have a chance to damage your weapon. It should not work with Power Attack, and be increased with Combat Expertise and Precision.
Suggestion #3
Shield revamp
Give shields % to avoid damage all together on their own, physical as well as magical. Granted your shield will suffer the damage, but a good adventurer will take steps to make sure they have the right tool for the job
Toughen up shields, hardness and durability.
Revisit named shields with resistance as well, give them some omphf! Maybe some absorption?
Summary
As you can tell I'm all about damage mitigation, and I say let the high dps play thier way, but also give the sword and shield community something to get excited about. We've all read stories about heroic fights, but I personally have enjoyed Bruenor's fighting style as opposed to Drizzt.
-paint