I do wonder with the change to the market board tax system ( no longer get a discount based on if you buy from the city a retainer is in):

What is the point of having retainers set to a specific city? Seems to me that it's yet another rushed band aid fix without much thought to the ramifications of other systems.

A system that has been in place at least since 2.0 when I started playing. Why have they determined that this is the right system to change at this time 5 years after the fact?
World visit caused basically everyone who cared enough about selling things to move their retainers to Limsa (or the Crystarium), so they either had to get rid of the tax or tax you regardless, and theyre certainly not going to remove even a terribly implemented gil sink.