It seems to me that current group dungeons and arenas are too easy once you get close to optimized load out. I can only imagine how easy they are once you have BiS. I can see a lot of good players getting tired of grinding these dungeons for alternate gear sets. As such I propose a third level of difficulty called Undaunted. On this level, dungeon specific set drop rates should increase.

With this new level there should be a new Undaunted pledge. Unlike the current pledges, these pledges should be selectable by the player and weekly. By selectable I mean the player gets to choose what content they will take on for the weakly. Set peramiters like time limit, no death, and/or other content specific requaiment. As a reward for completing the content you'll get a platinum (insert contents name) key.

The platinum chest will contain the contents specific loot table. The key will allow you to pull one item that is removed from from the chest until the chest resets. Every item removed from the chest adds X% chance that the chest will reset. This number should be relative to the number of items in the chest, whereas it won't reach 100% until the chest is cleared.

I feel this would make all the content that much more enjoyable for min/maxers that just want that right piece. This also gives average players like me something new to strive for.