I know DRG is kind of considered OPed now, but OPedness is transient.

Logically there is really no reason for DRG to take as much fall damage as say a WHM.

I would like to suggest that fall damage be absorbed by their TP bar. 100TP if falling from a height that would take off (100%-1) of a typical PC's HP (excluding NIN of course), it will then scale downwards, e.g. fall that takes off 50% of a typical PC's HP would result in a lose of 50TP for the DRG.

NIN takes less damage due to their metahuman level of physical conditioning.
DRG should take no damage due to their DRG training/technique - which consumes TP to negate fall damage.

To be honest, it isn't really that big a deal. Fall damage is not a big part of the game's combat mechanics. Any trait that reduces/negates fall damage is pretty much a gimmick trait.