This simple change would fix every problem with Warrior + Paladin Tanks since their purpose is to mitigate damage and not threat cap DPS. Everything else is fluff for parsing. This would allow devs to move on from this quagmire to balancing DPS and healing classes.
Every 2 points of Defense above 300 reduces damage from creatures by 0.15%.
Every 2 point of Defense above 300 reduces damage from players by 0.05%.
Double the block value on all shields as bosses hit for hundreds/thousands.
Discuss.