I feel like there are several things they could do to make a more permanent impact on the gil farming that's going on, but they seem convinced that just banning them over and over is actually accomplishing something.

Options would include:

Cutting off their primary source of gil by removing the gil drops from the trash mobs they farm.

Improving dungeon enemy AI so they reset if they can't reach their target, making them unkillable through less then legit methods.

Putting a killzone in OoB areas to prevent them from hacking to keep themselves safe.

Fixing whatever shoddy coding is allowing them to hack in the first place.