Dwarf Therapist is a gift from Armok.
Miner: I'm a traditionalist. One miner per 25 dorfs, and they're an elite force of rock-munchers, kept constantly busy doing something.
Engraver: Stone detailing only. Legendary rooms created by just making large rooms with fancy engravings in.
Smiths/craftsdwarves/mechanics/cooks/brewers: ONLY their specific labour enabled. They're legendary, and they create the good stuff. This is only for skills where quality of production is important.
Farmers: Only farming (fields). My food and booze supply is a major priority.
Hauler: One size fits all. Hauling labours, cleaning, furnace operation, masonry, carpentry, minecart haulage, butchery, food processing labours, and basically anything unskilled. And yes, carpentry and masonry are 'unskilled'. You don't need to be legendary to carve out blocks or construct a wall. And I may need beds RIGHT NOW. If I have any particularly skilled dorfs, then I'll set up some workshops with skill levels set for some fancy stuff to be produced. But, mostly, quantity > quality in most things. Especially haulage, with my attempts to automate it only meaning I do MORE of it. This is what takes up most of the workforce. The vast majority of them, in fact, because my dwarves need to stay busy so they don't get too attached to each other. Idleness breeds tantrum spirals, so I pursue the hoarding of assorted stuff. Mostly stone blocks, food, booze, and metal bars.
Medical staff: Only cleaning and hauling of wounded enabled other than their specialisation. My attempts to automate and streamline hauling tend to cause accidents.