It's a nice thought, OP, but then there are veterans who are just rolling through content to help out or doing a quest, and literally do not need any gear from the dungeons. I'm a 70 DPS rolling through a level 51 dungeon - I know my rotation inside out and, and I'm going to be passing all then loot anyway. Despite contributing 50% of the DPS for the whole dungeon, I'm not going to lot on anything. So it.... does nothing for anyone else.

Maybe if this was applicable to non-gear items, like minions or ponies/birds/dogs, but even then it's trying to solve a problem that really doesn't exist. If someone's performance is poor because their iLvl is low, they need the gear more than anyone else, don't they?