We are planning to have the number of rewards you earn vary based upon your evaluation.
I think it's been mentioned many many times that your 'evaluation' system simply does not work. It heavily favours certain jobs such as PLD and DNC whereas support jobs are generally evaluated poorly.

This is a huge part of the current problem with Walk of Echoes in that certain jobs can enter with you solo, spam abilities, contribute nothing to the fight and yet walk away with a 1st place chest.