I think it would be incredibly amusing if all endgame content had tiers of difficulty you had to go through. Lets take the ogre from DH for example.

Tier 1 (for just quest completion): regular tank and spank no bogeys no drop, beat that? Good time for lv2
Tier 2 Ogre WITH bogeys, obviously this would screw up all tactics for him as it should. Time for lv3
Tier 3 Ogre as it is now.

I think it would be interesting and fun to have endgame content expand on top of itself like that. Keep all the good gear for the hardest difficulty but add a step system all players had to go through. Each step would add new dynamics to the dungeon/area that completely screws up the tactics players built thus far. It would add extra life to the content and keep players on thier toes the whole time