If you farm NPC-s or just sell resources,you dont need tax rate att all,mine is on 0 always,keeps loyalty on 100,why should i even boder to make,what,500k or even a million gold per day from taxes,if i can get 500 mill a day from npc.Ok,i have to say,taxrate is usefull when you just started playing and have no means of attacking NPC and you need everything you produce for building.But later on its useless.