Lvl 1 enchanting shack on each toon for now*
I'd keep a lvl 1 enchanter shack for each toon until you reach lvl 100 and ilvl at least 600, probably even 615. It's easy to get to ilvl 615, but then the higher level drops really trail off.
Up to lvl 100 and ilvl 615 you will be getting so much gear that you don't need, can't use, and/or will upgrade, that is makes sense to DE all the WOD gear and sell the mats or send them to your enchanter.
Note that any toon that does not specifically have enchanting as one of its professions will never be able to DE non-WOD (legacy) gear. Even if you have a lvl 3 enchanting hut. Having the enchanting hut has nothing to do with having the enchanting profession. So don't level it up past level 1.
Not being able to DE your Pandaria gear as you level up through WOD is not a big deal, because DEs on Pandaria gear sell for next to nothing on the AH. Even sha crystals are going for 5g -- remember when they were going for 2500g? There's still a little bit of demand for Pandaria enchants -- up until ilvl 600, Dancing Steel and Jade Spirit are still the best enchants most of the time. But the mats for them (sha crystal) are so cheap that your enchanter can make them for 25g - 50g, but they will only sell from 75g - 150g.
Still a demand -- don't forget the people who are just now leveling up their alts and the new players. But the demand is very very low and not tremendously profitable. Worth your time, and profitable, but not hand over fist.
Then later on you can switch the level 1 enchanting hut out. Until then having a lvl 1 enchanting hut on each alt is a big moneymaker.
Mining and Herbalism You can absolutely drop mining because they are trash prices on AH, and also you get a mine. I'd even go so far as to say don't bother leveling up your mine.
You can also drop herbalism, but WOD herbs still make money because the herb gardens don't pump out nearly as many herbs as people need. You can make good money on herbs on the AH. I spend so much money on herbs that my next toon I am raising up has herbalism.
Tailoring Hand over fist moneymaking from Royal Satchel. Keep all your plats in Halfhill Market in Pandaria. Grow Motes Of Harmony. Motes and Spirits are no longer soulbound and can be bought on the AH. So that gets you around the daily imperial silk cooldown! That's also why windwool cloth often costs more now than it did at the end of Pandaria.
Get your most powerful AOE toon, get a potion of luck (or make it with your alchemist), and spend 20 minutes every day at the gash in the eastern center part of Dread Wastes, farming windwool cloth. Plus you can keep your eye on the AH for motes, spirits, and windwool, and buy when they are blue (during the week usually) and just stockpile them. An hour of that per day can get me enough mats for four or five Royal Satchels a day. If I buy 100% of the mats on the AH and then turn around and make Royal Satchels from them, I double my investment at a minimum. I always keep several on the AH, pull everything on Thursday and relist it much higher for the weekend only players. If I get most of the mats from farming them myself, I can get 5 or 6 times the cost of making them. Every now and then they sell for 4K gold - every couple of weeks I'll sell 5 to the same player for 4K each. That's at least 15K gold profit at about 400% markup. The hexweave bags in WOD are like the Royal Satchels were in Pandaria, with the cooldowns. They are so expensive that they're not worth the effort, just stockpile hexweave for your cloth alts. People who never bought Royal Satchels downstream their bags to their banks, so there is still a pretty big demand that won't go away for a while.
Blacksmithing is useless except to gear up your plate alts. JC is only good for making ilvl 540 rings that you can use as soon as you hit level 92. They are made with trash level ores you buy on the AH. You can sell them for 50 - 100 gold, but they cost 5 gold to make. Only ever make the level 92 ones and not the 95s and 98s. By the time they hit 95 and 98, everyone will have better quality rings from drops. The only other good thing with JC is, you can make the 92, 95, and 98 rings from trash ore on the AH all day long, send them to your enchanter to DE, and then sell the mats or enchants for huge markups. You can basically do that all day long. Even if you flood the market, your markups will be huge. Some days you'll get a 2x markup, but some days you'll get a 10x markup -- especially if you are considerate and sell the mats in maximum size stacks. I freaking hate people who put up 200 auctions of 1 Draenic Dust instead of ONE auction of 200 draenic dust. I can gouge the hell out of other enchanters if I put up max stacks for sale, and they can do the same to me.
Enchanting is the biggest moneymaker for me right now. Even though enchanting has been simplified, everyone still needs to buy new enchants as they progress. Tailoring is second place.