I think one of the main problems here, as Koltik mentioned, are players who exploit the system by farming an absurd amount of points by exclusively fighting non-experienced players while actively dodging real teams through constant monitoring of player activity on other servers.
It completely invalidates the intended purpose of the current ranking system when the highest ranked players point gains have entirely been from farming non-experienced teams 24/7.
If Stormblood ends up having the same ranking system as now, then Light Party rewards should indeed be removed if Square Enix cannot actively police the system.